re: How long should a TV Show Run

For dramatic shows I think 5 or 6 is the sweet spot. That gives plenty of time for characters to grow and for there to be resolution of a few overarching storylines w/o running out of ideas. LOST, Sopranos, X-Files (which went about three seasons too long) are good examples.

For a comedy there is more room. Since it isn't a drama, they don't need to "up" the intensity every season. Seinfeld went nine seasons and stayed pretty strong. Cheers was 11 seasons, plus another 11 for Frasier. I would say eight or so good seasons is pretty doable. The only exception would be if the sitcom includes kids or some kind of "coming of age" angle, then that puts a limit on the timeline.