Just food for thought: I recently had a high pressure plug crack and extrude the o-ring, at only 2000psi. I was surprised how much gas escaped in the brief time it took to shut off the valve. Luckily I was just kitting up in shallow water for a practice dive so no incident, but it was a wake-up call. The reg is about 15 years old. The head of the plug cracked along what appears to be a tiny microfracture that corroded internally until eventually failing. I've heard from knowledgeable folk that H2S corrosion is a thing, especially with brass. Not to say that regs shouldn't be rebuilt for a good long life, but after so many wrenchings and microfractures and hidden corrosion, at some point Murphy is dealing the cards. Also a good lesson to drill home the need for practicing gas supply failure skills!!! Just thought I'd share that experience. Onward.
The blind screw failure is an interesting anecdote.
I routinely carry an old 35 mm film canister with a number of HP and LP blind screws, to either alter hose routings; or to eliminate a gauge or another regulator, should that ever be desired. Over four decades, I have yet to experience the sort of metal failure that you've described; and that so-called "micro-fracture" of the blind screw, may well have been an issue with that equipment from day-one -- an outlier, not necessarily a function of its age.
In terms of the "wrenching," that you described, the proper level of torque required, is truly negligible among dive equipment assembly,
if done within manufacturer's specifications. A hose or a blind screw, typically requires 6 +/- 1 nm to seat, on a first stage, easily accomplished with an open-ended wrench; the screw, with the odd Allen wrench; a valve stem or valve housing cover, 28-30 nm, with a torque wrench, which can easily be pulled off -- also by hand -- with a first stage, held in a hand towel.
Beyond that, is simply excess; doesn't achieve a better seal; and any resultant damage, is not an issue of age; but, rather, of mishandling.
As far as that hydrogen sulfide issue is concerned, in terms of a regulator, you'd have to significantly flood that first stage of yours -- and, further, continue to culture a population of sulfate reducing bacteria, such as
Desulfovibrio, in a nice, moist anaerobic environment; and while I have seen damage from HIC (hydrogen-induced cracking), within the maritime and petrochemical industries, I have yet to encounter it within an even marginally-maintained, twenty-year old scuba regulator -- even those that I have seen, retrieved from marine salvage . . .