OFFILES Cleanup

Our Post offices OFFILES folders are full of files as old as 1997.
We have a weekly job to purge older that 183 Days on all Post offices (6 GW 7.03 Post offices)
Q1. What can I do to purge this stuff?
Q2. Is there a chance that it might actually be valid stuff?
Q3. If a user Archives mail, all of it including the attachment is actually moved to their Archive location isn't it?