I know there's so many threads about this but most are about ppl thinking to buy one. My friend had one in his closet that he never uses and said here you go. It's essentially new old stock luxfer al40. He bought it new ten years ago and hasn't dove it once. Needs a hydro has a pro valve. I'd like to start diving great lakes wrecks. And want a redundant supply for emergency only. I was originally thinking of buying a 30. But free is free. should I just use it or would I be better off posting it local and see if there's anyone out there who wants to trade a good 30 for a 40 ?