Regulators, at least quality regulators, are perhaps the ultimate in durable goods. Scubapro, Aqualung, Sherwood and until recently, Dacor were all companies that provided parts and services support for their regulators for decades. Mares really screwed up when they discontinued parts support for out of production Dacor regs as they lost a lot of extremely loyal customers when they did that.
High end regulator performance has also not really improved in the last 15-20 years with a quality top of the line 20 year old regulator performing to the same standard as a top of the line regulator made today. And in the case of Scubapro, they use a design approach that in most cases allows older regulators to be brought up to current standards.
In some ways older regs are arguably better as they tend to have more metal parts and tend to be more durable with less dry mouth.
And in another regard, older regs often offer performance advantages over new regs as many, if not most, new regulators are designed or at least factory de-tuned to meet European certification freeflow standards that usually turn a great regulator into one that comparatively breathes like a rock.
From a practical standpoint what has traditionally drove regulator retirement were changes in the number of ports on the first stage. One LP port and no HP port used to be standard. But the use of LP inflators and later octopus second stages led to an increase to 2 and then 3 LP ports and SPG use led to the incorporation of an HP port. People attaching regs to HP ports and blowing up LP hoses led to change in the size of that port. Eventually another LP port became standard to accommodate dry suit inflators and 2 HP ports became standard to accommodate hose routing tastes.
But if you have an old first stage from Scubapro, Sherwood or USD Divers/Aqualung with 3 (or 4) LP ports and a 7/16" HP port, the odds are that it will still prove very useful regardless of age.
In my case, I get things at dealer cost and justify the purchase of new regs for field testing and for familiarity for service purposes. But more often than not I end up going back to old reliables once the novelty wears off.
