Not sure how to answer your question really.
I had two imap folders and one pop. I've actually taken the plunge and created a new pop for one of the imaps.
The archive has been handled by autoarchive and as the inbox for the imap account got bigger I started to manually archive stuff into the archive box.
The archive box contains everything from the three accounts so I've started moving it into personal accounts according to various criteria. All a bit laborious. Anyway, point is, I have various pst folders - archive, outlook, imap account, new pop account. Outlook pst contains the other imap account and my personal pop account (I had no hand in dividing everything up like this, Outlook did it on installation!)
I can just copy the archive folder to the desktop as a backup. If that's a good idea...
??