Cooper Flagg led Duke to the Final Four and was a dominant force all season. He is ready for the NBA and should declare for the upcoming draft. Chris Carlson/Associated Press

Immortality has an expiration date.

Most of the time, there are signs. A soreness that lingers, making those jumps and sprints that were second nature a little harder. The realization that your phone’s flashlight is no longer enough to read the check in the low light of a restaurant.  Sometimes it ends suddenly, in a series of X-rays and MRIs and injuries.

Right now, Newport’s Cooper Flagg is immortal. He’s 18 and has a whole life of basketball dominance ahead of him.

That’s why there should be no question about whether he ought to declare for the NBA draft. Any talk to the contrary is either wishful thinking by Duke fans looking to hold on to something or from somebody peddling self-serving bad advice.

It’s time for Flagg to jump into a higher tax bracket.

This was part of the plan all along, right? Graduate high school a year early, where the challenge had waned, and get to college. Turn 18, and get to the NBA before the challenge of the college game goes completely stale.

Zaccharie Risacher, who went No. 1 in last summer’s NBA draft to the Atlanta Hawks, signed a four-year contract worth just over $57 million. The first two years of that deal are guaranteed for $25,766,760. Flagg’s deal, should he be the top pick (honestly, if he’s not, who is, and why did the team with the first pick screw it up?) will be about the same. That’s generational wealth.

Utah, Washington and Charlotte have the best odds of winning the NBA draft lottery on May 12. After that trio, it’s New Orleans, Philadelphia and Brooklyn. The draft isn’t until June 25, giving Flagg plenty of time to house hunt in whatever city wins the top pick.

Cooper Flagg led Duke in points (19.2 ppg), rebounds (7.5), assists (4.2), steals (1.4) and blocks (1.4). Ben McKeown/Associated Press

This season, Flagg led the Blue Devils in scoring (19.2 points per game), rebounding (7.5), assists (4.2), steals (1.4), and blocks (1.4). His fingerprints are on everything Duke accomplished this season. It would be hard to top that next season, especially with Cam Boozer scheduled to take over Cameron Indoor Stadium as Duke’s newest can’t miss phenom.

Many of those who mocked me a few years ago for suggesting we slow down the Flagg hype train and let a 14-year-old kid actually be a 14-year-old kid, to maybe not deify someone barely a teenager, are now shouting from their online soapboxes that Flagg is 18, he’s just a kid.

NBA teams have employed 18-year-old basketball savants for decades. They know how to build support systems for these young players. No matter where he begins his pro career, Flagg will be fine. We hope the ping-pong balls break in favor of one of the Eastern Conference teams, just so he’ll come to Boston a few more times each season instead of just once with a Western Conference club.

Some say Flagg should return for another season at Duke to “finish the job.” The job was never to win the national title. That would’ve been a welcome component of his continued basketball development, of course. But Flagg’s season at Duke was an internship designed to prepare him for his next job, and there’s no doubt that’s exactly how it unfolded.

Injuries can derail anyone’s career. Cooper Flagg missed the final two games of the ACC tournament for Duke because of an ankle injury. Those risks add to the list of reasons he should enter the NBA Draft. Chris Carlson/Associated Press

Yes, it was painful for fans from Maine to see the look of abject shock and sadness on Flagg’s face as the semifinal against Houston slipped away last Saturday night. It was so … abrupt. In those moments, he looked younger than 18, and yes, it’s warranted to spend a second or two hoping he’ll decide to return to college for one more season, to not let that be our final image of Flagg in Duke blue and white. It was as if Maine’s entire population of a million and a half people gave Flagg a mental hug at once.

The injury factor should not be dismissed. Flagg got a small taste of that in the Atlantic Coast Conference tournament. The ankle injury he suffered was minor, but it kept him out of the semifinals and finals of the tournament and should’ve been a 20-foot-tall neon warning sign. No matter how well you train and take care of yourself, this can all be taken away in an instant.

The Final Four loss should be his last college game. He would gain nothing from another year of dominating college players.

There’s a protective instinct at work with a number of Mainers when it comes to Flagg, and that’s admirable, even if misguided in this instance. Yes, he might have struggles in the NBA at first, playing against grown men with years and experience he needs to collect. If he struggles, it will not be because of lack of effort or talent. He already has those attributes. They’re just not going to develop at the college level any more.

So far, Flagg and his family have made the right decision at every crossroads. This one feels like a no-brainer. Take that talent to the next level. Maximize the potential. Immortality isn’t forever.