Awhile ago, I was part of the staff on a different forum then this one. We came up with an idea of keeping important threads that were closed in a whole different section.
Examples of what could be placed in there(what we had placed in there on our site):
Mod Applications.
Suggestions that were used.
Old rules.
Etc. (Anything that a new member could look at to get "caught up" with what has happened before they joined.)
Or, we could place all closed threads in the archive and pin the important threads. It would help out new members and it would help clean all the clutter in the forum. Again this is just a suggestion. What do you guys think about it?