TV shows
I propose that there are four five categories of TV series distinguished on the basis of how long they run and the quality, or lack thereof, of the show more or less objectively defined (to the extent that one can do that).
1: Shows that jumped the shark
These are shows that become redundant, lose their writing quality, or for some other reason reach a point where they get bad. That point is, of course, the "Jumping-the-Shark" moment. The phrase "Jump the shark" of course comes from an episode of Happy Days when Fonzie, water skiing, jumps over a shark. That was apparently a bad episode…