“Firefly was great - but no show should run forever.”
Give the man a cigar!!
Shows should run just long enough to tell the story — otherwise, they’ll morph into a soap opera, within 5 years.
It’s particularly important for serialized shows to complete the story — otherwise, viewers will be reluctant to start watching them, and really frustrated when they end abruptly. Unfortunately, the show runners just can’t leave well enough alone. If a show is getting good numbers, they make the plot more and more complex, and add in multiple soap-opera arcs (will they, or won’t they? oops, they did — now how long will that last? and so on, and so forth, ad nausium). Then, one day, they notice the numbers start to drop, and they end the program abruptly, without actually finishing the story they started out to tell.
Oh, and Firefly needed another 4 or 5 years.