Since failure of a Vac pump is almost a random occurrence, (some failures
reported within the first 10 - 20 hours and in some cases, 0 failures in
100,000 fleet hours) it's pretty hard to attach any significance to either.
But, and it's a big "but", it only takes one at the wrong time to bite in
the worst way.

I've never had one fail but someone I knew took off IFR (from the Santa
Barbara airport, where the departure was out over the ocean) and entered the
clag at about 500 ft. His vacuum pump must have failed soon thereafter
because he augered into the Pacific ocean less than 2 minutes after takeoff.

Only takes one and the first one may be the bad one.

Dan Schaefer