I pull mine as part of the run-up on every single flight, IFR or VFR. It is on my
run-up checklist.

Dave Butler wrote:

Said shuttle valve is also a point of failure. You can check it on the ground
with the engine idling. At idle, the manifold will pull more vacuum than the
pump. I can count on the fingers of *no* hands the number of pilots I have ever
seen perform this check routinely.

At risk of beating a dead horse, get the dual-rotor pump from
http://www.aeroadvantage.com instead.

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759