Media failure is a concern regardless of the backup method.  A failure
that occurs as a result of physical destruction of the tape is
probably not really critical because you (should!) know about it
immediately and be able to recreate the backup.  I wonder, though, how
good the philosophy is if you work on an incremental forever basis
once the backup media gets very old.

What is the useful life of tape media in comparison to the required
retention period of the backup data?

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