Wild horses couldn’t drag them away.

Mick Jagger fits into skinny jeans, and Tom Menino doesn’t. But, at 69, neither wants to give up his gig.

Leaving the stage isn’t easy, whether you’re a rock star prancing in front of 20,000 fans or a mayor lighting up a medium-sized metropolis with Christmas trees.

But a proper exit strategy is crucial, especially for people in the spotlight. The world remembers the last frame of their life’s work, and can be cruel when it fails to measure up to past performances.

Frank Sinatra is often cited as an example of the hanging-on-too-long phenomenon. At the end of his career, the legendary crooner needed a teleprompter because he could no longer remember the lyrics to songs he sang for decades.

But critics can also be wrong. The Wall Street Journal published a piece about Bob Dylan, which was headlined “When to Leave the Stage.” Describing the singer’s “always-raspy voice, now deteriorated to a laryngitic croak,” it read like an invitation for Dylan, then 69, to call it quits.

The iconic folk singer didn’t take the hint. Fans still flock to his performances; and a reviewer for the New Yorker called Dylan’s latest studio album, “Tempest,” “as spirited and vigorous an album as he’s made.”

When it’s over is not always obvious. Does Mariano Rivera want to go out as the greatest closer in baseball history? Or does he want to end his career throwing meatballs that hungry batters can pound out of the ballpark?

On one hand, the currently injured Rivera won’t know his fastball is gone until he tries throwing it in a pressure-packed ninth inning. But even then it will take something more — humility and a self-critical eye — to understand that it’s never coming back.

Philip Roth stunned literary critics when he recently announced his retirement.

Roth, 79, decided to stop writing in 2010, a few months after finishing his novel, Nemesis. He didn’t share his decision then, because he wanted to be sure it was the right one: “I thought, ‘Wait a minute, don’t announce your retirement and then come out of it.’ I’m not Frank Sinatra.”

To reassure himself, he reread writers he hadn’t read in years. Then he started rereading his books, from the last one forward, “casting a cold eye” on his words.

Roth said he stopped at Portnoy’s Complaint, published in 1969, and never got to his first four books. At that point, he realized, “I knew I wasn’t going to get another good idea, or if I did, I’d have to slave over it.”

A writer can change his mind at any time, and literary critics predict Roth might. His writing is still admired and marketable, even if some critics snipe that his recent work isn’t as strong as earlier novels. Roth is also healthy.

That’s an essential part of being able to deliver a kick-ass performance, whatever your line of work.

Health is Menino’s problem. The mayoral spirit may be willing, but the flesh is getting weaker.

Now in his fifth term, Menino must decide if he is physically up to a reelection campaign. A victory sends him to City Hall for another four years. Or he could win, quit, and hand the office over to an acting mayor. That’s how he got the job. Ray Flynn left office to become U.S. ambassador to the Vatican, and Menino, as City Council president, was next in line.

But to do that would deprive Boston of something it sorely needs — a noisy, free-for-all campaign that attracts a diverse field of would-be mayors.

Exiting is a personal decision for a Boston mayor or a British rock star.

Time is not on their side.

Jagger risks ridicule if fans find his crepey skin too creepy. But music is always moving forward, and it moved past the Stones long ago. Boston’s next riff starts only when the Menino riff ends.