Keep the URL's where they are and the topics where they are. Nothing ever has to be moved. Just show the topics based on last date something posted to it.

If last_post_date > 10 days, topic is not shown unless user is in archive mode (provide a link or button at the bottom to turn it on/off). Or perhaps just [More...] (since we are unix fans) to see the "archived" topics.

And when you add searching capabilities, you can even add a checkbox to indicate if should search the "archived" topics, or just a field to indicate how far back to search.

You could actually make this thing configurable per user with default of 10 days ("consider topic archived when no activity after __ days"). You could have forum and system level defaults as well do you don't need to hardcode any value. Archiving is off if there is no user, forum, or system setting.

This has the following benefits:
- each user can have their own preference for archiving.
- archiving is dynamic and automatic.
- no extra archiving forums.
- accessing archived topics is easy.
- URL's don't ever change.
- archiving will not affect current discussions (this was a problem at IWE).

What do you think?

Well, if there is no post in any topic in a forum for so long, the forum need not show up either, unless you press [More...] (or whatever) at the bottom of the main IWETHEY board page.
The nice thing is, if all of a sudden there is new activity in a post or forum, it shows up again with new posts to read! Ain't that nice??