One mechanic told me if you're replacing either the regulator or the blower motor, to do them at the same time even if one is fine. He said in the case of my regulator, the reason it only lasted 100k was maybe because I put in a new regulator but not a new motor at the time, then the regulator is responsible for turning an older motor that doesn't spin as freely as a new one.

Certainly makes some sense that it's possible.