I would hazard the guess that it was simply piss-poor maintenance and not the age of the regulators, per se, since the symptom of what you were describing was probably a torn or improperly-installed diaphragm; and should have been noticeable at pressurization.
Two years between overhauls has become a standard among many manufacturers; but that interim, should be based soley upon its rate of use, and not the calendar . . .
At one scientific company, years back, I was responsible for about sixteen regulators -- the oldest of which, were approaching thirty years; and the youngest, four to five years.
All were well-maintained and overhauled on an annual basis; there were no failures; and all of the rubber "consumables" were replaced when something showed obvious wear; or, during overhauls.
It is just a matter of regular maintenance and nothing more; and I would have been willing to use any of them, at any depth . . .