I know what you mean about television shows dragging on long past their best - I love Buffy with all my heart, but I think it went downhill a lot after Season Four (although I will defend it to the death, I cannot find it in me to love Season Seven, however hard I try), and it's been the same with a lot of programmes I love. (I do still watch ER, though. And like it.) And here is a chance to be irritatingly smug about my country - I think, because of the BBC being mostly funded by licence fees rather than by advertising, producers of BBC shows find it easier to end things on a high*. As people invariably bring up when this kind of conversation starts, Fawlty Towers only had twelve episodes and is still hugely popular; more recently, The Office and Extras both had just thirteen (including Christmas specials) and are again really popular even after they've ended. If more writers felt they could stop while they were still ahead, it would probably lead to much better television.


*of course, we also have vast amounts of crap - most US exports manage to be much more popular than our attempts at drama - and many shows that have been going on for ever, but still. Moment of national pride.