President Obama and Michelle Obama head to Marine One on the South Lawn of the White House in September 2013. (Mandel Ngan/Agence France-Presse via Getty Images)

Ahhhh, the post-presidency! Our commanders in chief are always rhapsodizing about their retirement years to come.

“We could play some dominoes together,” President Obama suggested wistfully to the soon-to-retire David Letterman last week. “We could, you know, go to the local Starbucks, swap stories.”

We’ve heard this kind of chatter from all our lame-duck presidents, a wink at how great it will be to get out of Washington, relax and let someone else lead the free world for a change.

But the days when an ex-president and his wife could step off the world stage and retreat into private life are long gone. Like their recent predecessors, the Obamas are quietly devoting some of their final months in the White House to laying the groundwork for a very busy life after it: a free-form career that is expected to be very public, very active and — owing to their relative youth — very long.

In a video announcing that his presidential library would be built in Chicago's South Side, President Obama discussed the personal importance of the city, saying he "became a man" when he moved to Chicago. (Barack Obama Foundation/YouTube)

On Tuesday, the president’s foundation is expected to announce the location of the Barack Obama Presidential Library, which early reports have indicated will be on the South Side of Chicago. And the president and first lady have started giving some hints of their plans following the next president’s inauguration on Jan. 20, 2017.

“I’ll go back to doing the kinds of work that I was doing before — just trying to find ways to help people, help young people get educations, help people get jobs, help bring businesses into neighborhoods that don’t have enough businesses,” Obama recently told a group of middle school students. “That’s the kind of work that I really love to do.”

Chicago, where Michelle Obama grew up and her husband began his political career, is where his presidential foundation is already based. But unlike Harry S. Truman returning to Independence, Mo., the Obamas have said they may remain in Washington until their younger daughter, Sasha, completes high school. Associates have suggested that the first couple may make a more permanent home in New York.

The president recently announced that My Brother’s Keeper, the White House program he established to help young men of color, will form an independent nonprofit organization that will raise money from corporations. Michelle Obama’s Let’s Move campaign is already affiliated with a nonprofit independent of the White House. The president and first lady also recently launched a program to boost girls’ education around the world, in partnership with the State Department and the government of Japan. Any of those programs could be part of their post-White House work.

While taping the interview with Letterman, Obama told the talk-show host that he plans to take off only about a month after leaving office.

The Obamas’ moves are part of the ongoing evolution of the lives of ex-presidents, said Burton Kaufman, author of “The Post Presidency: From Washington to Clinton.”

“In the old days, presidents died after they left office,” Kaufman said. Teddy Roosevelt, Calvin Coolidge, Dwight D. Eisenhower, Lyndon B. Johnson — none survived more than a decade after their presidencies. Ronald Reagan, suffering from Alzheimer’s, lived quietly in California. “What presidents do now,” Kaufman added, “is they make lots of money.”

President Obama joins former presidents George W. Bush, Bill Clinton, George H.W. Bush and Jimmy Carter at the dedication of the George W. Bush Presidential Library and Museum in Dallas. (David J. Phillip/Associated Press)

That evolution has been a crooked path. George Washington retired to his plantation, as did Thomas Jefferson, who also spent his time building up the University of Virginia. They both remained involved in politics, but just a little, Kaufman said.

But John Quincy Adams ran for Congress in 1830, the year after he left the White House, and served in the House of Representatives until he died in 1848. Andrew Jackson also remained very active in politics, in a manner that would today be deemed uncouth: To keep his successor Martin Van Buren from regaining the White House in 1844, he actively backed James Polk, who won. And when Benjamin Harrison returned to his law career after failing to win reelection in 1892, those who faced him in court balked at going head-to-head with a former president.

What was the young nation to do with these men who had held such immense power? Grover Cleveland, the 22nd and 24th president, wrote a joking letter to a friend during his last year in office: “And still the question, ‘What shall be done with our ex-Presidents?’ is not laid at rest; and I sometimes think [newspaper editor Henry] Watterson’s solution of it, ‘Take them out and shoot them,’ is worthy of attention.”

Lawmakers once mulled strategies for keeping ex-presidents off the streets — giving them a job, such as an ex-officio position in the Senate or an informal role in the Cabinet. Those ideas fizzled, and the ex-presidency instead became a time for former presidents to focus on their legacies.

To do that, presidents must raise money, said Julian Zelizer, a professor of history and public affairs at Princeton University. But the easiest time for them to do that is when they are still in office — which, for all the good intentions and worthy causes, “will naturally raise questions,” he said.

Mark Updegrove, director of the Lyndon B. Johnson Library and author of “Second Acts: Presidential Lives and Legacies After the White House,” said a modern-day “president can make a few speeches and line his coffers and ensure financial security in a way that Harry Truman couldn’t have imagined and wouldn’t have participated in.” Truman thought accepting money from corporations would tarnish his former office. Gerald Ford, who needed to earn a post-White House living, caught flak for joining corporate boards.

Those kinds of questions are being raised about the fundraising juggernaut that is the Clinton Foundation. Bill Clinton has been an unusually successful charity fundraiser in his post-White House years — though much of that success, involving overseas donors with questionable business practices, has been uncomfortably proximate to his wife’s bid for the presidency.

Yet the ambitions of the Clintons’ global foundation have a clear antecedent in the later years of another former head of state: Jimmy Carter. Carter, who has written more than a dozen books engendering healthy royalties, raised money to build an institution to promote his policy agenda.

“He is the beginning of the modern post-presidency,” Kaufman said.

The former president uses the Carter Center, which describes itself as “a nonprofit public policy center founded to fight disease, hunger, poverty, conflict and oppression around the world,” as his base of power. Through the center, Carter has remained a very public figure — often deeply involved in international relations. In 2002, he was awarded the Nobel Peace Prize. Just this week, the 90-year-old was in Guyana to observe elections there. He cut short the trip after falling ill.

A former constitutional law professor, Barack Obama has said he loves teaching. And he can always look to the model of William Howard Taft, who left the White House to become a law professor at Yale — and was later appointed to the Supreme Court.

The future for Michelle Obama is less obvious. As the first presidential spouse to have her own social media accounts, she’s not expected to retreat from public life completely. But will she follow the model of Eleanor Roosevelt, who became delegate to the United Nations — or Betty Ford, better known for the founding of the alcoholism treatment center that bears her name than for anything she did as first lady?

“Once you remove some of the security and political constraints one operates under in the White House, the possibilities are enormous — particularly for first ladies,” said Carl Sferrazza Anthony, a historian with the National First Ladies’ Library. “I think that is a really intoxicating recognition.”

Michelle Obama and Laura Bush participate in a forum at the U.S.-Africa Leaders Summit in Washington last year. (Gary Cameron/Reuters)

Last year, Laura Bush spent a little time with Michelle. Bush came away from their encounter feeling that the current first lady was already dreaming of life after her husband’s presidency. Bush, who has traveled more frequently and kept a higher profile than her husband since they left the White House in 2009, knew the feeling.

“When I first came home, I said, ‘I didn’t realize I was under so much stress when I lived at the White House,’ ” Bush told The Washington Post then. “Those first few weeks at home I would get in bed at night and think, ‘Oh, now what do I have to do tomorrow?’ And then I would take this deep breath and think — ‘I don’t have to do anything tomorrow.’ It was sort of nice, but it’s still great to be able to work on the issues that were important to us, and we’ll do that for the rest of our lives.”

As Laura Bush knows, the modern bully pulpit is ever available for former presidents and their wives, but how to use it is up to them, said Katherine Jellison, a professor of women’s studies at Ohio University, whose research includes first lady studies.

“They are always going to be celebrities, but when they stay in the limelight they leave themselves open to criticism,” Jellison said.

White House aides are reluctant to speak publicly about the Obamas’ future. They would like the conversation to remain focused on the 21 months the president has remaining in office. But part of what makes the modern post-presidency unique is that it has become a virtual Round 2 for presidents, said Brandon Rottinghaus, a professor of political science at the University of Houston.

“It reflects a wish list of what they wish they had done in the office,” he said.

The health-conscious Obamas, who will be in their early 50s when the president’s term ends, could be working through their wish list for decades.

“They get the best care ever, and they live for a really long time if they are well,” Anthony said.

So, the proper salutation when this first couple leaves the White House won’t be “goodbye,” but “see you around.”