i have a crossfire that is about 11 or 12 years old. Been sitting for 8 years, I just rehydro'd it and used it. It works great with no issues of shoot down or anything.
I will say though, the old regs and tanks are LOOONG! I am getting another tank soon just because the new regs/tanks are almost 2 inches shorter!! In retrospect I would have been better off just chucking the tank and buying new.