There are a lot of times when you go to forums and they say to look for an existing thread for a certain topic rather than create a new one. I don’t think it’s a bad thing to revive old threads, unless they’re like several months old and several pages long. It would take a little while to go through it and refresh your memory.
If you’re talking about people reviving old topics to boost their posts for admin, though, yeah… that sucks.