You would never look back!!
Come to think of the plastic gearbox on the 80 window motor, I found that there was more resistance in the gearing.... which led me to think that the plastic had deformed slightly and was causing more drag as such on the motor and hence a possible added strain. The alloy gearbox on the 70 version felt quite a bit freer.
So with the sticking window rubbers and the possible deformation of the plastic gear housing. Of course the auto up/down is also the culprit that would finish off the motor!
An observation