Senior Senator Kay Bailey Hutchison (R-TX) works with staff before a television interview in the Russell Senate Office Building rotunda on Capitol Hill Thursday, March 29, 2012. (Melina Mara/The Washington Post)

It’s another season of uncertainty for lawmakers waiting to complete year-end work and wondering when, or if, they’ll ever get home for the holidays.

That’s the one part about serving in Congress that Sen. Kay Bailey Hutchison (R-Tex.) will not miss once she leaves next month. The Lone Star State’s senior senator is leaving after nearly two decades of service, and retirement means no more rushing home on December weekends to quickly buy and wrap gifts and trim the tree in between last-minute votes on health-care reform, treaties and the impending “fiscal cliff.”

“Being here on Christmas Eve when your children still believe in Santa Claus is a very hard thing,” she admitted. With two 11-year-olds at home, “What I will not miss is not controlling my own schedule, being on 24/7 — which you are — always on call for the emergency of the moment, or the thing that needs to be done, whether it’s a hurricane in your state, or a tornado or a hostage in Iran. It’s always something that pulls at you that you signed on to do.”

Hutchison’s retirement comes at the moment of a milestone in the Senate: She is the most-senior Republican woman in the Senate, but she will not be among the record 20 women who will serve in the chamber next year. The historic number of women could have been higher overall — and for Republicans — if Hutchison and Sen. Olympia Snowe (R-Maine) had opted to run again and had won. (With Hutchison and Snowe’s departure, Sen. Susan Collins (R-Maine) will become the chamber’s most-senior Republican woman.)

Snowe is leaving because she’s frustrated with the increasingly partisan nature of Congress. Hutchison is leaving for more practical reasons: She is an advocate of term limits and is eager to return to the private sector.

“I do believe that it’s a great, great opportunity, it’s a great experience, but there is a time to come and a time to go,” she said.

Hutchison, a lawyer, is expected to return to her legal roots and plans to write her third book, this one about Texas history. In 2000, she co-wrote “Nine and Counting,” a book that chronicled the work of the Senate’s nine women.

Hutchison briefly served as the fourth-ranking Republican, at that time the highest Senate leadership position ever held by a woman. She left the spot in order to run unsuccessfully for Texas governor in 2010 and because of the demands of the job, but she said that with more women serving in the Senate and politics at every level, “everything’s open now.”

“I think we will have a woman president, I think we will have a woman minority or majority leader, and I’m very optimistic about the role that women play and the leadership capabilities that we’re seeing coming up from the states,” she said.

In her closing weeks, Hutchison has unveiled a plan to provide a way for the children of illegal immigrants to apply for legal permanent residency. Her Achieve Act differs from the Democratic-backed DREAM Act in that it would offer only legal residency if eligible people complete military service or higher education and have worked in the United States for at least four years. Many Latino advocacy groups oppose the bill because it fails to present options for citizenship. Sen. Marco Rubio (R-Fla.) — a leading GOP voice on immigration issues — is not a co-sponsor and is working on different proposals.

With immigration likely to be the signature domestic political flashpoint next year, Hutchison said that lawmakers should avoid doing a large comprehensive overhaul of the nation’s immigration system, noting that previous attempts to do everything at once backfired.

Working to pass bills on residency or citizenship opportunities for younger illegal immigrants, guest worker programs and border security “would lower the number of the last thing that you would have to deal with, and that’s the people who came here illegally and the amnesty issue,” she said.

Texas likely sits at the forefront of whatever is done to address the nation’s immigration concerns — and Hutchison said that shifting demographics there should serve as a reminder that the state “is very culturally advanced.”

“The perception is that we’re cowboys, kind of yahoo oilmen that got rich but didn’t have much education or that sort of thing. And of course it’s absolutely not true,” she said, adding later that “I always like to say that a lot of people think that Texans are a little loud, we have a little too much fun, but remember — our hearts are as big as our mouths.”