An archival copy is what I have too....
normal board:
http://themepark.nl/ubb/archive
http://tpkc.nl/archief/Even got myself a dusty logo/color scheme
I fill up the archive automated, topics move to the archive forum after X days of non-replying (can be set per forum). And I can manually keep topics like in ubb 6.5.x if I don't want them moved. I can select which forums are pruned.
The keep/unkeep topic stuff is a hack in ubb, the rest are extra scripts and cronjobs. Archive+life board don't have to on the same server, pulling the data from the liveboard is an action done by the archival copy. So you can have that archive locally.
I have not published this one yet, kind of a lot of work and I didn't see any demand for it.