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For those who don't know, the regulator Art is showing is a Scubapro Mk VII, which has a "sonic" reserve on it. With every breath, it rings out a tune telling everyone within ear shot that Art is getting very low on air.
Absolutely nothing wrong with a good working J-valve. I have about a dozen old steel 72's and have at least 4-5 j-valves. If the dive store doesn't understand them, you may want to find another shop. Some shops are great people but technically clueless. If they are working on your gear, they really need to understand it - and really dive equipment hasn't changed all that much, it only takes a little "correct" research to know what's what. If they truly believe it's a safety issue, they don't know and you probably won't get anywhere arguing with them if that's their mindset.
One trick I've used is, if you have your own compressor, fill the tank snd then vent it quickly so that the valve is frozen. The temperature and dimensional differential between valve and tank neck will sometimes loosen a stuck valve.