Cheap gearboxes (DeWalt and Globe) for Offseason project

[dbonar]

I hate to reply to my own post but I have a related question.

Is there any way to tell how much a given gearbox could be expected to survive? There are loads of 12 and 24V gearmotors sold for less than $20 that could have their motors replaced, if they would survive much higher rpms and torque than what was expected with the original motor.