> Our library is an *intelligent library* and we handle all 
> cleaning thru it on a time basis, not mounts.  [...]
 
This is _so_ not recommended.  [1]

> able to determine the lowest usage point of all of our drives per
> library in each 24-hour cycle and for each day of the week.  
> We then set
> up drive cleaning on a time basis, instead of mounts. It's worked out
> nicely since drives are nice and fresh and clean to start the backup
> cycles :)

And worn!


[1] the last cart/cassette drive I know of that was supposed to be
cleaned on a frequency basis was Exabyte 8mm drives up to the 850x.  And
_those_ were based on tape motion time, computed by the drive firmware.
Can't remember any drive where mount-time-based cleaning was
recommended.  Well, maybe the refrigerator-sized 7- and 9-track drives
of the late '60s through the '80s... weekly PM, drive teardown and
cleaning, all that wunnerful 91% isopropyl alcohol.

HP Ultriums (and others) have strategies to protect the drives from
their owners, including _not_ running the cleaning tape if you put it in
unnecessarily, and a little bitty brush that cleans the head instead,
and cleans it after a cleaning cartridge is run.

For anyone with too much time on their hands, try Google on something
like "dlt drive cleaning head wear abrasive" and draw your own
conclusions.