Just buy a simple $20 intermediate pressure gauge from almost any good dive source. Check your regs every few dives while on the boat and watch the readings and needle creep. It's really to easy. As your regs start to needle creep, it will give you plenty of more dives to decide if you want to service them or buy a new stage. Yes you can mix brands. An IP gauge will be the best money you have ever spent and provide you with a knowledge and comfort that your regs are safe to dive that day. It's exactly like checking your car tires. If one of your car tires reads 25psi, you'll say "well it's not flat, but I might want to have it serviced this week" That's how an IP gauge works. I wouldn't wait til the 1st stage seat blows when you pressurize it cause then you are either going to have a $30 quick rental charge or you just blew a ton of time, gas & boat fees to sit out the dives. Same thing, why wait to come outside in the morning to a flat tire?
