Well, there were a couple of questions unanswered above. I just bought a Dacor Pacer 900 on e-bay for just over $50 (with shipping). I've looked at it, and it is a great older regulator (not old, just older). This is a third-generation regulator, and of solid brass, it will wear well. I bought this one to replace one that I gave up in the 1980s, and it was a great buy (complete with an octopus, LP inflator and SPG).
The questions unanswered:
--How will I know it's going to fail? Well, first these regulators do not fail to a no-breath situation; they fail to a free-flow situation. So if there is a catestrophic failure, there will be a trickle or a surge of air. Now, this applies to the 1980's regulators. There was a recall for the pruge button that, according to the notice to NOAA, would potentially cause a no-air situation (which I still have not figured out). There were pre-1979 regulators, and there was a Dacor-initiated recall of it.
--It is unlikely that the High Pressure (HP) seat will crack or be scored, as is suggested above. But I liked the suggestion to keep the purge down as the valve is opened; that is probably good advise for any regulator.
--Most likely, the only thing that needs to be done with your regulator (and mine) is a lubrication/replacement of any O-rings in the unit. The HP diaphragm should also be examined, and perhaps replaced (if it is stiff, for instance). One O-ring on my second stage was flattened and came apart when I took the hose off, so all O-rings need to be examined/replaced.
--The regulator, even with the service, should be used. It's a great-breathing regulator, and probably still has many years of service left. I would not be looking to replace it because of need anytime soon. Consider replacement if you find another regulator you like better, is better cosmetically or ergonomically, or offers some other advantage you cannot receive from the Dacor Pacer.
SeaRat