There is a treatise of accelerated aging of organ leathers, including
testing a wide variety of leathers as old as 150 years old.  This
was published by Organ Historical Society years ago and may be out of
print now.

For testing purposes you may cover a wind motor in the cloth to be
tested and run it continuously on a suction pump at full speed.  This
is the way we have tested things in the past.  For heavy bellows cloth
you may cover a Duo-Art or Ampico pump and run it 24/7 with most hoses
plugged.  I prefer a Duo-Art pump for this since it does not have a
spill valve.

At one time our shop had a Duo-Art pump just recovered with PPCo brown
cloth and had it on the bench using it for testing other things.  After
several hours of use per day, it went from an original pressure of 120
inches WG to a maximum pressure of 20 inches.  This is how we discovered
a batch of bad cloth made in the early 1990s.  The cloth had stretched
and the rubber had not.  Only one week of full time use had exposed this
problem.

D.L. Bullock
www.dougbullock.ws