3 Bad Alternators in a Month

If it was the electronic parts of the alternator failing, I would chalk it up to bad parts. But the bearings failing, I would look at too much tension on drive belt, or misalignment problems. Also check alt for not having any movement when bolted up.

I dont think it would be an alignment problem since my factory alt lasted for 18 years and the bearings in it were fine when it went out. What is the best way to check for alignment? I still have the stock tensioner, could it be getting weak and leaving too much slack causing bearings to wear out?

Bearings wear out when there is to much tension on the drive belt.
I doubt that you are getting brand new alternators from Autozone or elsewhere. You are most likely getting remanufactured /rebuilt units from these places. A suggestion could be to replace your tensioner, I believe GM still makes new tensioners, If you are interested ,I have a good one
with about 50k miles on it from my roadmaster. A new Delco alternator from GM will cost you about $450 dollars. If you dont like the sound of that then I would bring you old alternator to a local starter,alternator ,generator rebuild shop,where they have people
repairing units that actually know alot about what they are doing! ed