I think removing thread expiration might increase activity, as there are some old threads that I know I, and at least a few others have looked back at and have expressed wanting to reply to now with the new knowledge that we have gained since then. I understand that this can contribute to spam, however I think it would overall increase activity. Perhaps we could implement it something like we have implemented how new members post: mods have to approve any posts in a thread that has been dead for over 2 months? I don't know, just something I'd like to see.