Alternator problem

I replaced the battery and the alternator last month. I will be going on my third alternator. The first one was bad from the store and the one I have on the car now I had them test it before I left the store. Most recently I went to visit a friend that lives 2 hours away from me. The car ran fine no problems but once I got there, I turned the car off. Maybe 45 minutes later went to turn the car on the car was dead. Once I got back home I charged the battery and found out the alternator was not working again.

What would cause the alternator to stop working within a month?

Where are to motor to body grounding straps?

What else should I be looking for?

Any help would be great. Thank you