Sorry, I must dissent.
While there are things that irritate me (and I won't go into them here since I want this to be short and focussed), one of the things I like is that threads remain open for update (when information changes) or addition (the "Who we are" thread of baobab's) and are automatically brought forward every time a new posting is added. While I will agree that some seem to go on and on long after the point is exhausted, that seems to be a problem of self-control with some of the posters (and what is wearisome nonsense to one reader may be amusing light banter to another).
The only reason I can see for arbiitrarily shutting down threads is the loading time it takes for a long versus short thread. However, once loaded one can rapidly get to the bottom of things by judicious use of the "end" button. (There seems to be endless potential for puns in that last sentence, doesn't there?)
Anyway, while it may make sense to limit the breadth of a given topic (new "coupon trade" threads monthly, for example), the fact that threads remain open is not that major a matter to me.