Luckyzach

So I’ve recently had to change my battery because it had went bad but the battery itself wasn’t but a few years old. I own a 2002 Pontiac Trans Am M6 with a sound system, 150Amp alternator and high output battery wires. Whenever I have the car turned to accessories, it reads normal voltage, between 12V and 14V. But whenever I start the car, it reads between 15V and 16V. I asked a couple people and they think that with higher output alternator, the battery is boiling water and killing the battery. But I’m not entirely sure. I was wondering about what I could do to fix the issue. If I go back to the stock alternator, it has issues whenever I turn the volume up to a certain point. Headlights dim and other small things. But it works great with the high output alternator. Is there something I can add to the system to keep the battery from dying every few years or do I need to just buy a new battery every couple years?