I do not quite understand the question.  There are many pieces to the
question is the DR volume set good?

1)      Are we backing up everything for the DR set that we think we are?
2)      Are we doing storage pool copies correctly to create the offsite
copy?
3)      Are all the tapes in the offsite vault?
4)      Do we have the correct database backup for the restore?
5)      Is the media good?

I am sure there are other questions that should be asked.  However, I think
this sets the stage for the question points.

The audit volume will test the media, but that does not mean it will
necessarily read again at the recovery site.  Maybe 2 sets of offsite copies
are necessary for your business to feel comfortable.

Ultimately, the database backup is very crucial, two copies of it are
probably prudent.

There comes a point of trust in the hardware.

If you have enough money, you can get pretty close to 100% certainty of
being able to recover.  The question is how many 9s are good enough.  Each 9
you add will have a logarithmic increase in cost.  In your business, not
being able to recover timely means you are probably out of business.  You
may want to thing about other technologies such as remote disk mirroring
(hot site).