I think there is a simple solution that has worked for me for the past few months. I am using Top Cog brand belts for all 3 belts. After replacing alternator after alternator, I finally just tightened the crap out of the alternator belt so that there was 1/4" deflection or less. It turns out that the belt was slipping almost all the time while driving, whether I could hear it or not, and I wasn't charging the battery as a result. This left me stranded a couple of times.
After tightening the belt up, I drove 2 days normal driving and then retightened to 1/4" deflection. After that for the next month, I retightened it every week. Now it has seemed to stop stretching and is charging correctly.