Because of the size of our database, I've decided that now would be a good time to split it into an "active" database and an archive. The archive will contain completed games (moved over on a regular basis in the future) and non-active threads in a read-only format, and eventually I think we'll be able to modify the forum code so that you can view threads or search in the archive more easily than having to go to a "separate" forum.
Part of the purpose of this is to reduce the size of the "active" database. We're pretty big, and I expect many sites our size have multiple servers and databases to handle the load.
Regardless of how things are split, nothing currently on the forum will be lost - I'm not going to be deleting anything from the current database, just copying. During the transition process, the phpbb2 forum will remain viewable, primarily for Notes and Private Messages. Notes are a jeep-mod, and we may not be able to easily convert them, but you'll be able to view them here to save a copy locally.
Private Messages will probably be pruned significantly on the active forum - on the test I just pulled, I only copied PMs if they were in the past ~4 months or saved, and that was still over 70k messages.