So you all know this phrase, “jumping the shark,” right? If by some chance you don’t, it refers to a particularly egregious episode of Happy Days in which Fonzie enters a competition that involves jumping his motorcycle over a shark tank. The phrase itself, however, has come to refer to an episode of a TV series that marks the beginning of the end, the moment when the series begins its long descent into cancellation or irrelevance.

Usually when a series jumps the shark it’s because the writing declines or the actors get sick of their roles or the show as a whole goes to pot. But I’ve decided it’s also possible for a series to jump the shark simply because it’s run its course. And in that case, it’s time for the series to go, even if the writing, acting, and production values are still right up there.

This thought occurred to me while watching season five of Burn Notice. Now Burn Notice used to be one of my favorite shows. I loved Jeffrey Donovan’s multiply talented Michael Weston. Gabrielle Anwar’s Fiona was the perfect combination of strength and vulnerability. And Bruce Campbell was, well, Bruce Campbell. But the basic premise of the show, Michael trying to find out who framed him and trying to be reinstated as a spy, could only go on for so long. Even the introduction of a new player, Cody Bell’s Jesse Porter, couldn’t keep the idea going past a certain point. And by season 5, I was feeling restless. Yeah, yeah, sinister forces out to stop Michael, criminal mastermind, blah, blah, blah. Anything else on?

I’m afraid the same thing is happening with another of my favorite series, Leverage. As with Burn Notice, I love the cast. But the premise, Nate Ford’s band of merry confidence tricksters, is beginning to seem tired. There are only so many ways to introduce conflict among the players and most of them have already been tried more than once. I’d say it’s time to find a graceful way to end the crew’s adventures.

The sad thing about these shows is that they haven’t descended into mediocrity—they’re still doing good work. It’s just that the premise the shows are based upon is wearing out. Time to suck it up and quit while you’re ahead.

I’ve seen terrific shows stay on a little longer than they should have, and the results aren’t pretty. I loved The Wire, for example, but that final season was so much weaker than the others that I almost wished they’d just skipped it. I stopped watching The Sopranos a couple of seasons before it ended because I was tired of Tony and no longer interested in the evils the family indulged in. In both cases, the series had reached a peak in the fourth season—the wonderful, heartbreaking examination of the school system in The Wire, the jolting plot with Ralphie in The Sopranos—which they never really equaled. If the shows had ended then, most of us would have grieved, but we might also remember them fondly as shows that went out on a definite high.

I guess the point is that all shows wear out eventually. Right now I’m waiting breathlessly for the next season of Justified, but I’m sure there will come a time when I’m no longer as entranced by Rylan’s adventures as I am now. The tough part for the show’s producers is figuring out when they need to put their creation out of its misery (the fact that that creation is the source of their livelihood must make this decision even more difficult). Still, tough though that decision may be, it needs to be made. I’d say it’s time for Michael Weston to stride off into the sunset, preferably with Fiona on his arm.