I saw many replies in threads that were inactive (without any replies) for many years. I don't know if this is feasible, but it would be nice to disable the ability to reply for threads that have been inactive for 'x' years. I'm guessing that people don't always look when the last reply was posted. Replying to a thread that is inactive for many years is kind of useless (specifically in the 'tech' threads).
Just because a thread is older doesn't mean that there can't be something new added to a discussion at a later time, so I'm just not convinced that closing a thread after a preset length of time would be in the best interest of the members.