There have been a lot of complaints about the durability of the motors posted in this forum. When two motors went out on my Alias within a short period of time, I jumped right on the bandwagon.
However, after reading a LOT of posts here, I started to pick up some good advice: don't 'stall' the motors. In other words, if a rotor cannot freely spin, kill the throttle. Looking back, this makes sense.
During my basic electronics training while in the AF, I learned that DC motors will pull more current if their rotational speed is less than it would be if its rotor was allowed to spin freely. Since the components in the motor are not perfect conductors of electricity, some of the current flow will be converted into heat, and the more current flow, the more heat.
I've also seen a lot of references to the brushes. While I don't know the exact engineering considerations, I do understand that the brushes are necessary to provide a current path to and from the rotor. If they're fragile, well, that could be the 'Achilles Heel' where the motors are concerned - heat will damage them.
Solutions? I have two suggestions - more robust brushes is obvious. The other has to do with the pilots - swallow your pride and kill that throttle when you crash, or even if you're about to crash. Don't power up again unless you know the rotors can spin freely.