The real question is what is your business requirement?  Forget what you
have done in the past for a moment and ask your customers what their
business recovery requirement is.

        If they could recovery a file from forever ago and it changed once a
day there is a large cost to do that.  Most customers will say they need
something for up to 3 years ago.  We arbitrarily presume we can just save a
yearly or monthly tapes and get back what they want.  Let's say they created
a file and worked on it for March 10th through March 25 and needed to keep a
backup of it for 3 years.  Let's just say now you saved every full backup at
the beginning of every month.  This file would be completely lost if it got
accidentally corrupted or deleted before April 1.  So, who is the fool in
this scenario when it is discovered 3 years later.

        TSM avoids all of this, you have a deleted file policy. You have
retention versions and a way to expire versions that get really old.  But,
it always keeps the copy that matches the active backup on disk unless you
as an administrator delete the file space or expire directories you do not
want using an exclude.dir.

        This all said.  You probably are looking at time as being your
retention policy for inactive versions of a file.  The only question is how
many versions of a file does a user think they need to go back to.
Remember, with TSM you can use different management classes for different
data on the same client and manage it differently.

        So, to answer you more directly.  Think about a very long deleted
file expiration time and a lower number of retain deleted versions.  Think
about NOLIMIT (or large number)for the number of versions and a period of
time that reflects your recovery requirements.  No matter what you come up
with if you use some kind of backupset type of thing you will lose a
customer's data eventually.  It only saves a copy of the current active
data.  You will need a copypool to send your data offsite with TSM, meaning
at least 2 tape drives and probably a lot more tapes, but the recovery
capability will be immearsurably improved.