James,
I'm interested to know too what Brenda says-or at least that's who I'm guessing it is since she's our regional engineer and you're not too far away from me.
In any case, I've had a couple of E2M2s that have sprung oil leaks after almost exactly 10 years of service backing a 597x MS. Usually they will still maintain ~40 millitorr(at moderate flow rates) for a few years after they start leaking, but do manage to make a mess.
I've seen larger Edwards pumps run a lot longer.
Of course, as dated as they may be, I still am rather fond of my old Welch/Sargent Welch roughing pumps. Of course, I don't have ANY now that are backing instruments, but there are a whole lot around on Schlenk lines, rotovaps, and doing other "dirty" work. They just seem to keep trucking along with an occasional oil change. I did an internship in a lab as an undergrad where were pumping down a few dozen samples a day that had been dissolved in CS2, and I don't know when anyone had last bothered to change the oil on the pump. I took the initiative of changing the oil. Initially, we were getting 30+ torr from a vacuum gauge directly on the pump inlet, and more like 100 torr by the time it made it through the(bad) plumbing to the rotovap. The initial drain that came out was a biphasic mixture of sludge and something that looked(and smelled) like a nice solution of the lighter fractions of the pump oil and CS2. I did three oil changes that day, with about 20 minutes of run time on the intermediate ones, and watched the vacuum drop through the day. When I wrapped things up, the pump was not only a lot quieter but would manage 10^-2 torr at the outlet(I redid all the plumbing and was able to get 1 torr or a little less at the rotovap). I did change the oil again on my second to last day at that job, as the vacuum had started to deteriorate a bit. It wouldn't surprise me if it hasn't been changed in the 12 years or so since I last did it... Of course, that pump lived a MUCH harder life than anything on a mass spec sees-it just amazes me that it came back to life so well after so much neglect.