Upon noticing a new rash of resurrected old threads, I was reminded of this idea I had once but forgot about.
How about, when posting to a thread that is older than the three month time limit, having vBulletin throw up an alert, something like:
“You are about to post to a thread that is older than our three-month limit. In cases like these, the SDMB recommends that you start a new thread with a link to the old thread. Do you wish to continue? Y/N”
Seems like the date of the thread is stored in vBulletin somewhere, otherwise you couldn’t sort the search results that way. A simple check on the thread date and then an alert wouldn’t be that difficult from a Dev perspective. Assuming the software allows for it.