Using multiple cleaning tapes successively

I agree.  Put in one tape and let it get used until about half of the cleans are used up, then add another cleaning tape to the library.  NBU will then alternate which one to use, and one will be used up before the other.  OpsCenter can altert you when one is completely used up.

Or you can script and schedule a job to warn you when the number of cleans left on a tape reaches zero. I think there is something like this in the .../goodies directory.

edit: yup, there is a "cleanstats" script you should be able to schedule to show all of the cleaning tapes and when the drives were last cleaned.