Faced with a solved, closed thread that wanted bring up, I would open a new thread. This idea is actually implemented on sites like StackExchange. They also close saying: This thread has been closed to further replies because it has attracted low quality answers. This is what usually happens when a thread has been archived after a time; people come in later and introduce off-tangent, irrelevant stuff. If a reasonable time limit after the last comment could be introduced where it is then closed, that would stymie spammers.