I have seen the following feature in another forum that also uses vBulletin,
it shows a warning for very old threads and you can only post an answer if you tick the checkbox.
I think it would be useful since i have seen many users reopen very old threads, maybe some of them don't even notice that they reply to old thread,
a message like that (and action required to continue) would probably reduce the amount of replies to old threads.
View attachment 53231
Alex