You should be able to tell how long the verify takes from looking at the job logs.
All verify does is read the tape, compute checksums, and then compare them to checksums written to the tape, it does not actually compare tape to disk
Many modern tape drive use read-after-write to do the same thing on the write pass, and will post errors if the data appears corrupt.
As long as your boss is satisfied with monthly test restores, they should suffice