Hal,
There are several things that can go wrong and I think that the bearing issue is way down at the bottom of the list.
The motor brushes can wear out.
The motor box can get flooded with water
The circuit card in the motor box can corrode.
The power cable can corrode itself right on to the motor box pins.
I suspect there are many other things that can go wrong that I am not familiar with.
Personally, I see no reason to plan for a failure that might not happen and if it does, then open the box and see what has failed.
Thanks,
Jim R.