Did "Stay Tire" load test your battery or just look at it? Most auto parts near me will do a free load test in the parking lot. It seems batteries today don't last over 3 years, and I have been replacing many in my vehicles and trailers lately. A month ago, I went back to Auto Zone with one, tested bad, and I recalled it being fairly new. Turned out I bought it just last April. The guy said it might have been sitting on the shelf too long (I'd guess the currently high prices do that). Anyway, still under full warranty.

My tip-off is first that the Battery Brain (on all my cars) trips off (its purpose is to save enough juice to start the car). I then put it on a charger, and if it says fully charged in too short a time (say 15 min), I suspect it isn't "holding a charge". I then take it in, and invariably it fails the load test.

People argue widely on the best brand to buy. I understand there are only 3 manufacturers in the U.S., for ~50 brands. In my limited research, people seemed to diss Walmart's Everstart brand at a higher rate. Could just be perception, but some claim their's are made to poorer spec's, perhaps how they can sell them cheaper than others.