This is not a story about ratings. This is a story about shows that have overstayed their welcome.
Shows like Glee, House and Grey's Anatomy are still pulling in respectable ratings, but are a shadow of what they once were. For every show like Freaks and Geeks, Sports Night and Party Down -- great shows that were canceled too soon -- there are series that risk their ultimate TV legacy by staying too late at the party.
Here's why Dexter and six other once-terrific shows are past their prime in primetime.
That twist in Sunday night's episode -- which we won't spoil in case it's still sitting on your DVR -- gave us pause for a moment. Could this be the thing that turns season six around? Nope. The season's still a mess.
Writers have Dexter Morgan tackling religion and where, or if, it fits into his life.
A guest stint by Mos Def as reformed killer Brother Sam was the highlight of those efforts, but everything else about season six has fallen flat.
That includes the return, sorta, of Dexter's dead serial killer brother; the painfully cheesy therapy sessions for Deb; the embarrassing way the writers have completely decimated Maria LaGuerta; and the mind-boggling reason Dexter has all of a sudden embraced killers like Travis and Trinity's son, Jonah.
If Dexter had been a lesser show, around season two or three viewers might have started to question the fact that there seem to be an awful lot of serial killers who a) live in Miami and b) always seem to cross paths with Dexter, even outside his police duties.
Darkly Dreaming Dexter, the novel in which the Dexter Morgan character was introduced, has become Deeply Disappointing Dexter.
He's been in jail and rehab. That's fine if you're, say, playing Iron Man. But if you're a doctor, the go-to diagnostician, this is not the resume you want to present to your patients.
Add in the many, many cast changes, and the fact that the show has fallen into a formula of bringing Hugh Laurie's House to the brink of redemption, only to see him embrace his inner jerk once again, and the diagnosis is clear: After this, the show's eighth season, it is most definitely time for House to be surgically removed from the Fox lineup.
The first season of the show was something new and different and fun.
The second season -- it was kind of like that kid you knew in junior high who came back from summer vacation for the first year of high school and had outgrown his awkward phase.
His sudden popularity went to his head, and he became a bully who was berating the Foo Fighters and Kings of Leon because they wouldn't let him play their music on his show.
And he kept relying on stunt casting like Gwyneth Paltrow and Britney Spears, shifting focus away from characters like Jane Lynch's Sue Sylvester, who, in season one, had already secured herself a spot among the all-time great TV characters.
Glee, by that point, had begun to drink its own Kool-Aid -- or slushies in this instance -- and creator Ryan Murphy's media fights with rock stars were just the most public proof that the show had become too self-important.
Of course, it is important, and wonderful, to see diverse characters on TV, especially for younger viewers. But it is possible for people to not enjoy Glee and its many musical interludes and still support the show's point of view.
Popularity and show quality don't always go hand-in-hand, but it is worth noting that the most recent episode of the show is down 2 million viewers from the third season premiere.
4. THE SIMPSONS
The Simpsons writing staff, on any given day, could probably throw away more good jokes than most comedy writing staffs could come up with in a week. Even in its 23rd season, the show is still funny.
But it's also tired.
We know these characters in and out at this point, from Homer and Bart to neighbor Ned and supporting Springfieldians like Comic Book Guy and Squishee-slinging Kwik-E-Mart owner Apu. While there was a sweet spot when that familiarity allowed writers to do things with the characters that tickled fans, now it just means the show never feels fresh anymore.
And by the time The Simpsons hits its 25th season -- it was renewed earlier this year for its 24th and 25th seasons -- we're going to be longing even more for those earlier years when the show could still surprise us.
5. GOSSIP GIRL
Doesn't it feel like Gossip Girl has been on for longer than five seasons? Yeah, that's not a good thing. Soapy dramas have to walk a fine line between too little action and piling on so much drama that the storylines and characters become tedious and unbelievable.
GG has hit the latter point.
Was it the Blair/Dan flirtation that sent the show hurling towards jump-the-shark status? Serena's affairs with her teacher and Nate's married cousin (and Nate himself)? The Blair and Chuck breakup and her eventual engagement to a prince? Jenny dealing drugs? Dan's novel? Yes, yes, yes, yes and yes.
6. 30 ROCK
Like The Simpsons, 30 Rock is still pretty funny. And also as with The Simpsons, we feel like we know the 30 Rock gang pretty well as the show prepares to debut its sixth season in January.
Familiarity often opens comedic possibilities for a sitcom. But all it has done for 30 Rock is open the door to make the characters even more outlandish, and to repeat the same jokes about them over and over. We get it -- Kenneth the Page is backwards, Liz Lemon is perpetually single and career-obsessed, Tracy is crazy, Jenna is pathologically selfish, Frank is gross.
With Alec Baldwin -- who rightfully snagged lead comedy actor Emmys for what were the show's two best seasons -- continuing to say season six will be his last, it's time to enjoy the antics of the show, and the show-within-the-show, for one more season. And then let's send 30 Rock off to that big cancellation heap in the sky.
7. GREY'S ANATOMY
Grey's Anatomy has had so many casting changes that we literally can't remember who's still on the show sometimes.
Earlier this year, series creator Shonda Rhimes tweeted the current season would definitely not be the series' last.
That's too bad.
And there's been so much partner-swapping, overwrought drama and McDreamy pouts over the problem of the week in his relationship with the angst-addicted Meredith that it's difficult to believe so many viewers have stuck with the show this long, its eighth season.
The Denny/Izzie brain tumor storyline alone would have done some shows in -- and that was back in season five.