Michael,

Having first accepted the brave assumption that there is no "user
owned data" for which there is a business mandate for retention (i.e.,
trusting that your users always store "corporate" data in the places
they are supposed to), my personal preference would be to keep backups
of deleted files (RETEXTRA, one copy only after deletion) for no more
than 90 days.  I would also tend to keep no more than 5 extra versions
of active files (VEREXISTS) for about 30 days.

I can't offer a particularly good justification for these numbers,
but, since we are only talking about personal, not corporate, files I
think it is reasonable protection for active data and against
accidental deletion.

If you change a file daily, you will have a copy from every day this
week and if you haven't noticed a major foul up in that time well....
 Similarly, if you haven't needed the file for three months from the
time you deleted it, you probably won't ever need it again.

What is very important, however, is that all users are notified of the
policy.  If they are aware of the current policy, then it is even more
important that they receive notice far enough in advance that they can
retrieve required backup copies to ensure they are backed up under the
new retention regime.  (Don't forget some users may be away on holiday
when you start the notification process.)

Murray Nicholas
IT Systems Consultant
Galeforce Information Services Pty Ltd
email:  murray AT galeforce.bu.aust DOT com