I "manage" a couple forums for friends (support forums with the same "disease" that has disabled me) ... and I am real strict about not posting to threads that have been dead for 120 days or more. I find it just messes things up and confuses things.
Someone "resurrects" an old post ... people respond thinking its a new post & then they find out they've already responded to the post months or years earlier.
I do have a mod that notifies people a post is 120 or more days old ... but that doesn't seem to stop them from posting.
So I verbally jump up & down about it ... and suggest if they want to continue the thread ... make a new post with a link to the old post. It works for a wee while ... until we get a rash of new members & it starts happening all over again.
IOW ... if you are "anal" about it (like me) you can literally drive yourself nuts every couple months until everyone gets used to the rules ... OR ... save your sanity and don't worry about it.
Personally ... saving your sanity is the better option I think. Its too late for me though