I always figure there's a lot less to go wrong in
a DLT cartridge than there
is with a hard disk
The flaw in this argument is the time it takes to make another copy, which needs
to be done at some point to migrate to newer media.
You will only know the DLT has failed when you try to read it again.
If you care about the data, it should be kept in a form that is easily replicated
and verified, and you should assume that any single copy of that data WILL become
corrupted or unreadable over time.