A verify job can be run at any time that the data still exists on the tape. A Verify job just reads the data, then computes a new checksum for the data just read and compares this new cheksum to the old checksum that was originally written to the tape with the data. This assures that the tape is readable.
A Verify job does NOT compare the current contents of the tape to the original source (disk) material. So if you were concerned that a verify job would fail as soon as something changed on the source disk, you do not need to worry about that.
