I haven't seen this feature yet, so I'm gonna put it out there.

phpBB has this auto-prune feature that you can set for forums.
It will prune every (insert number here) days topics that havent been viewed for (insert number here) days or posted to in (insert number here) days.

I really like that feature and would like to see it in IP.Board please. :)

I use this hook for 3.0.x and used its equivalent for 2.x for years.

http://www.devfuse.com/forums/topic/2480-m30-delete-old-topics-100/

Bump for forum auto-prune. This needs to be an integrated feature of IPB.

I am still using the hook with nary a problem.