Can you share some of your experiences in a little more detail?
I had heard that rebuilts typically last only 1-2 years but it is difficult to confirm and I do not understand why this would be. There are only a few failures that can occur in a motor:
Windings: Once these are gone, it does not pay to rebuild the motor.
Bearings: Once replaced, they should be as good as the original.
Capacitor: Again, once replaced, they should be good as the original.
Centrifugal Switch: Not all motors have this but again, should last as long as the original.
However, my theory is that many motor failures are due to bad bearings which in turn are due to a bad seal in the pump. If the motor is replaced without replacing the seal, then the same problem will occur again in fairly short order.
Another issue that is hard to detect is a bent motor shaft. If the motor is rebuilt and used again in a pump, then the seal new or not may fail in short order causing the bearings to rust and freeze.
So the short life of the motor may not have anything to do with being rebuilt, the problem could be that the tech did not properly repair the cause of the original problem. But that is just a theory.