That's my thoughts. "All that work" and Harbor Freight do not go together all that well. Considering that's what, 5 of them now, I think he'd be much better off just paying more for it and not worrying about the burning up of each weak motor/. Then he could work faster, longer, and likely more uniformly (though I'm not saying he needs to do more, he just needs something that could without dying).
5? Sheesh. I haven't been watching this thread / been here that long. I'd assume he's just trying to get too much done in one sitting and the motor is giving out under the heat. (and man does he get a lot done)