When it comes to serial entertainment, everything will end at some point. I’m sure even Superman and Spider-Man comics will cease someday. A show can end before or after it’s run out of things to say, but it’s worst when it hasn’t finished speaking.

We’ve all seen shows that kept going long after, by any rights, they should have been cancelled. Is there any doubt that Voyager only lasted 7 years because it was Star Trek, on a studio-owned network, and the previous two Treks had also run that long? “The Far Side” and “Calvin and Hobbes” ended while the artists were at the top of their form. Compare that to “Peanuts,” whose last 20 years were hardly worth reading, or the new “Opus” from Berkeley Breathed (although it does have its moments).

Most arc-driven TV shows work on a season-by-season basis, since TV shows are usually renewed one year at a time. Unfortunately, they also tend to like using cliffhangers to make sure the viewers come back. This works fine when you know you’re coming back, but there have been many cases — Blake’s 7, VR.5, and Farscape, to name a few — where the expected continuation never happened.

I don’t mind it nearly so much when a good episodic show ends. Like “Calvin and Hobbes,” it can at least have a good send-off. (“Live fast, die young…”) As much as I’d like to see more, it’s better than watching it slide downhill. It’s with the arc-driven ones, particularly those that still have more story to tell, that it’s especially annoying.

VR.5 and Crusade are good examples of this. Both were shows that made it through maybe half a season and were building up interesting storylines. The final episode of VR.5 answered some questions, but took an “everything you know is wrong” approach to one of the central mysteries of the series. Suddenly Sydney and her family were players in a much larger game, and it was no longer clear what the sides were.

Crusade, similarly, was working up to its actual story. Internet postings by series creator JMS and, later, two unproduced scripts that he posted to a fiction site (no longer available), made it clear that the original premise — finding a cure to the plague that threatened to wipe out Earth — was only a reason to get the crew out there. Unlike VR.5, it wasn’t ratings that killed Crusade, but studio politics. It was cancelled before it even aired.

At the point I heard about Angel’s cancellation, I wasn’t terribly disappointed. Maybe it was the fallout from Illyria, maybe it was just that I knew they’d have time to at least wrap things up. Unfortunately the last few episodes were sub-par. It was clear they were rushing to tie up every loose end they could think of, and I really wasn’t happy with the ending. (One more episode, just %$#! one more.)

In retrospect, I now realize that Farscape was very lucky to have been cancelled when it was, and not at some other time: they had completely finished filming their season finale (unfortunately a cliffhanger, but they were acting under the assumption that their two-year renewal really was for two years and not just one), which meant that they couldn’t hack up the scripts and compress things. Like Angel, they were told during a hiatus, but the run had left off with an absolutely top-notch episode, “Unrealized Reality.” Fans were energized, not demoralized, and a year-long fan campaign nailed Henson the funding for a miniseries. (Imagine if they’d left off one week earlier, with “Coup by Clam!”)