good idea though.
This.
And it puts relevant, current threads down in the page listing, which isn’t that huge of a deal, but if it happens all the time, an old thread can take the place on the front page of a current thread. The same thread might also already exist (as in the general RPG forum where there are two threads circulating asking what is your first RPG — one is 4 years old, one is more recent), and then you’ve got two rolling around, and no one really knows which one is good to post in.
It’d be nice if something did come up that could say "This thread is x months old, the person(s) you are responding to may not be active members at this forum any longer, or there the same topic might be found in a different, more recent thread. Are you sure you want to post?" I doubt it’d be that easy to implement.