There is the regulatory, or legal, aspects of keeping data around too long.
 Just ask Bill Gates about having backups of mail messages.  Instead of
setting it to retain forever to see how long people ask for things, work
with your customers to determine what there restore requirements really
are.  For restoration of data within 90 days, use backup.  For restores
(retrieves) of data older than that, consider archives.  And then only
archive the data that must be retained, and in a format you will be able to
read at the end of the archive's life.

Kelly J. Lipp
Storage Solutions Specialists, Inc.
www.storsol.com
lipp AT storsol DOT com
(719)531-5926