Has anyone checked the starter ?

I have a '93 Nissan Pathfinder, currently 210K on it. At around 200K, its original starter finally gave up.
Miserable job w/o a lift, so had my mechanic replace it, and he uses NAPA.
1st NAPA replacement failed in a few weeks (wouldn't hot start/re-start).
2nd NAPA replacement is now failing, same deal - fine cold, but hot days or conditions, NG.
Every relay, cable, ground, switch, charging component & battery is known good.