I bought my first regulator in 1966, a Calypso J, it still works just fine and I still occasionally use it. About the same time I was given a Mistral DH regulator which was manufactured in 1956 and I still dive it. I have Conshelfs (XIV) from as early as 73 I still use and prefer often. My Jet Fins are circa 1980-4?, not exactly sure and they replaced ones lost I bought about 73. My SP109 regulator set I put together some years back dates from the 70s and it is a very good regulator set. I have one wing that dates to 1984 which I still use, a Seatec, and I have spgs that I still routinely use from as far back as 73.
To answer your question, regulators from AL, SP, Atomics, Apeks and a few others are likely to be serviceable possibly for decades. BCs, it is a bag of air, I do not get to attached to a cloth bag, they last a few years, maybe a few decades, who knows. My favorite BC ever, I used it off and on for thirty years, then it fell apart. Wetsuits, a few years before they look like crap and stink too bad to dare use.
The USD RAM is from 73, the USD spg I bought in 73, the SP console I bought at a shop I worked in about 74 and the Tekna depth gauge I bought circa 1986, the USD Calypso riding shotgun is mine from (since) 1966 bought at a feed and seed store in Louisiana by me. I rode to the f&s store on my Raleigh 1964 English Racer to get it, about 20 miles one way. No big deal, I rode that far regularly to get feed for my menagerie of animals I had:
Some people think they need the newest and therefore think it best, I prefer older because I know it better. But maybe that is because I am getting older and better.
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