Rachel Maddow is the host of MSNBC’s “The Rachel Maddow Show” and author of “Drift: The Unmooring of American Military Power.”

In this 11th year of the longest armed conflict in U.S. history, it is starting to feel as if we may be near the constraining edge of an American war’s natural life span. The massive and lethal U.S. military is theoretically capable of sustaining itself in war almost indefinitely, as long as it is given the resources and the orders to do so. But as we close in on the 4,000-day mark ahead of our own fall elections, the inertia of the war in Afghanistan seems to be giving way to concerns about the costs of sustaining it and the need to find the best way to end it. Why now?

Our wars’ life expectancy has been bolstered over the past generation or so by a series of changes that eased the small-d democratic tensions that an American war abroad could cause here at home. The financial cost of war was for years taken off the books and treated as a fiscal asterisk, an “emergency supplemental” to the real and debated budget. The ranks of the deployed were bolstered with employees of private firms, obfuscating the cost associated with their services, the lines of accountability for their actions, and their number and individual humanity when they became casualties. For years, even images of U.S. military casualties were shielded from public view.

Three months before 9/11, Americans were given a multitrillion-dollar tax cut. After the attacks and our invasion of Afghanistan, not only were the cuts not rescinded but we gave ourselves another giant round of tax cuts less than two years later, just weeks after we’d shipped troops off to a simultaneous war in Iraq. While military families have endured multiple year-long combat deployments over the past decade, we civilians have endured something approaching the opposite of sacrifice on their behalf.

In politics, the Congress that got up on its hind legs after Vietnam, and insisted on seizing its constitutional prerogative to decide when the country went to war, dropped down to all fours and mostly ceded that authority back to the presidency. The decade-old congressional authorization to wage war in Afghanistan directs the military to go after those who attacked us on Sept. 11. Worthy as the current Afghan mission may be, the multibillion-dollar, multiyear effort to train Afghan security forces is at most an effort to protect us from a future 9/11, not to avenge the last one.

“The constitution supposes, what the History of all Governments demonstrates,” wrote James Madison, “that the Executive is the branch of power most interested in war, and most prone to it. It has accordingly with studied care vested the question of war in the Legislature.” Yes, it is unwieldy for a committee of 535 to make America’s decisions about warfare, but constitutionally that was supposed to be a feature, not a bug. A president given sole authority to decide on war may take the greatest care to debate and weigh his or her options, but that debate is executive, and private. A congressional debate occurs by necessity out loud and is conducted with an eye toward the feelings of the rest of us, one 600,000-population congressional district at a time.

The frictionlessness and invisibility of modern warfare for the American public represents a drift off the course set for us by the Constitution. It has made wars easier to start but, perhaps more important for us now, has also made them harder to stop. It has almost normalized the condition of America being at war. But even an inured public has a limit, and maybe 4,000 days is it.

At this time in the 2004 election cycle, public opinion on the Iraq war tightly matched party affiliation: Broadly, Democrats were against, Republicans were for. Today, public opinion on Afghanistan is much less rigidly partisan. Sen. John McCain and the George W. Bush-era hawks are still banging the drum (often in this space), but not all Republicans in Congress and even on the presidential hustings are humming along.

It is a caricature of war to say it starts when it’s declared and ends when one side wins; we have not “declared” war in 70 years, and real-world conflicts don’t conclude neatly with a big “The End” and rolling credits. Wars end through an agreement of some kind, even if (in rare cases) it is one side’s surrender. Whether and when to seek an agreement, and therefore a way home, is as much a political decision as it is a military one. And political decisions in America are made by democratic means, through our representative government, in consideration of we the people’s broad views of our national interests. Our public and political willingness to accept the costs of the Afghanistan war in years one through 11 (so far), may not hold for years 12, 13 and beyond. If so, it should not be lamented as a failure of will on the part of the American people but, rather, as an expression of our will.