Why you have "Necromancy"?
I don't understand how you can have "necromancy" issues to begin with. Why not simply auto close threads after a period of inactivity?
Many forums encourage users to search before posting to avoid duplicates, it's obvious that people here are not paying too much attention to the date of the last post once they find their topic.
If the threads were auto closed, once found they would see they can't reply so they would make a new thread without making you waste time.
i5-2500, Asus p8p67le, 8g ddr3, gtx460. Eeepc 701 4g surf.