For decades, the professional life span of an NFL quarterback was the same: He’d ascend in his mid-20s, peak a few years later, continue to dominate in his early 30s, and then, shortly thereafter, start the inevitable slide toward a television gig or car dealership. But that’s changed the past few seasons, sparking a new team-building debate that’s coming to define this era.

Even if only one or two quarterbacks were hurtling toward being functional after 40, it would represent a considerable sea change in the NFL. But there aren’t one or two; there’s an entire generation, forcing numerous teams to reevaluate their personnel strategy and mull what to do with a quarterback who’s managing something that, until recently, had never really been done before.

Ride him until the inevitable catastrophic season? Take short-term gambles on draft picks and free agents despite not knowing how long the QB’s window will remain open? Cut the aging passer prematurely and spend the cap dollars elsewhere?

No one knows, and there’s a reason: There’s almost no history from which to learn.

There have been 15 instances in league history in which a player 34 or older has posted a QB rating above 100 while starting double-digit games. Nine — nine! — of those have occurred in the past five years. Steve Young was the only player to do it twice — until Tom Brady, Drew Brees, and Peyton Manning all did it multiple times. Carson Palmer, who will turn 37 this season and was last seen torching defenses for a career-high 4,671 yards, will assuredly join them as a repeat achiever, as will Tony Romo if he manages to remain healthy. Great quarterbacks under 30 certainly exist — Cam Newton and Russell Wilson are both 27 — but the top eight players by passing yards per game last season were all north of 30, a feat never equaled in the NFL.

This is particularly notable in light of the dilemma currently facing the New Orleans Saints, whose quarterback, Brees, is 37, a year away from free agency, and almost comically expensive at a $30 million cap hit. He also happened to lead the NFL in passing yards last year.

To further complicate matters, since 2012 the Saints have employed a salary-cap strategy that has maximized their spending in an apparent effort to win now, in Brees’s prolonged prime. But, erm, how can they know how long that will last? Pretty much anything is on the table these next few years. Normally, most NFL contract talks are boring. The vast majority of star courtships play out with the same tension as the film Titanic — we know where we’re headed, but not how we’ll get there. But Brees has outrageous leverage: Due to collective bargaining agreement mechanics, his 2017 franchise tag would cost more than $40 million, so he can force a longer, more lucrative deal or leave town if the Saints decide to cut their losses. This is the decision many teams will face: With the going rate for quarterbacks climbing (the top 11 most expensive players in salary-cap dollars will be quarterbacks this year) the team that bets on an aging passer is going to have to bet big even though the wheels could fall off at any moment.

Teams have a tendency to make weird mistakes when there’s something new to navigate — the salary cap, evolving technology, rule changes — and this is no exception. Fans and media members sometimes scratch their heads when Patriots coach Bill Belichick makes a move for the future, even as Brady’s 30s tick away. But Brady’s prime apparently lacks an expiration date, and Belichick’s policy of cutting veterans, trading down draft picks, and doing slight rebuilds every few years while Brady continues to thrive is paying off. Brady, who was 38 last season, averaged two passing yards fewer per game in 2015 than he did during his historic 2007 season, when his team went 16–0 in the regular season and became the poster squad for unstoppable offenses before losing in the Super Bowl.

The Saints, Cardinals, and Giants (who have 35-year-old Eli Manning) are operating as if they must win now, approaching every offseason aggressively. The San Diego Chargers, oddly, seem in no hurry to maximize their window, even though Philip Rivers is 34. The Packers, Steelers, and Bears have quarterbacks approaching an age when observers will start to predict a decline — but at least by then they will have a blueprint on how to handle their team building.

Certain changes to the game reinforce that this is a trend, not a fluke. For one, there are the ever-loosening passing rules, which have led to an unprecedented rise in passing numbers. Pass interference and illegal contact penalties have made one-on-one defensive coverage a nightmare for even the best defensive back. Quarterbacks have amassed 4,900 passing yards in a season 13 times in league history — 11 of them occurred in the past five years and 12 occurred in the past 10. Then there’s the sports science: Brady’s regimen is so legendary he has a now-famous “nutrition manual” available for purchase (though it’s currently out of stock on his website). Packers quarterback Aaron Rodgers, who is 32 and has cut dairy from his diet, recently said he took tips from Brady’s routine to lose weight.

What’s more, while there’s long been a parade of platitudes about football being a mental game, rule changes have made that increasingly true. The 2011 collective bargaining agreement limited how much teams could do in the offseason and how much hitting they could do in practice during the season. This month, Palmer painted a picture of the modern NFL offseason routine as almost a purely mental exercise — ”I’m kind of just pretending,” he said, noting that because players can’t touch anyone or even come within a certain distance, he has to imagine that receiver is facing press coverage, for instance.

This may seem like a small rule change designed to make players’ summers easier, but NFL decision-makers say it has created an environment in which older players can flourish more easily: There’s less mileage on their bodies and their intellect allows them to take over. For years, conventional wisdom held that the early 30s were the pinnacle for a quarterback, who was still healthy enough to move and finally smart enough to make all of the passes. Now that healthy period is being extended and the smarts are being heightened.

Aside from freaks like Brett Favre and Warren Moon, quarterbacks have followed the same template for years: Joe Montana led the league in passer rating at 31 and 33 and was pretty much done after age 34. Dan Marino peaked in his mid-20s, led the league in yardage in 1992 at age 31, then slowly limped toward the end of his career. Jim Kelly soared at 30 and 31, then got progressively worse until he retired at 36. Steve Young dominated at 31 and 33. John Elway led the league in passing in 1993 at age 33, his best season, but by the time the Broncos won back-to-back Super Bowls in 1997 and 1998, he’d cut back on his production in favor of the run game. Brees and his peers enjoyed great success in their early 30s, too; those spikes have just happened to continue for the better part of a decade.

Peyton Manning, once the patron saint of old quarterbacks, is now their cautionary tale. After his two best yardage seasons ever came at age 37 and 38, Manning collapsed under the weight of his own career in 2015 and was just about the worst quarterback in the NFL during the regular season, throwing nine touchdowns and 17 interceptions and battling injuries until a heroic defense led him to a career-capping Super Bowl appearance that, even in victory, reinforced that it was time for him to step aside.

Even so, Manning made it to 39; he was in position to fail despite multiple neck surgeries that are far more serious than the injuries that plagued Brees (shoulder), Brady (knee), and Palmer (knees) in the past.

Now teams must hope that they can treat quarterbacks like movie studios treat comic book franchises: get a star in place and try to keep him there for two decades. The new era of quarterbacks is here, and no one knows how long the trend, or the players who’ve sparked it, will last.