318is wiper motor burn out

My grandson has a 91 BMW 318is. We have replaced the wiper motor on it twice in about 3 years. The first replacement was a "rebuilt" but that was actually just a paint over. The second one was new. It lasted about a year and then quit parking correctly. About a month later the motor actually burnt up while he was driving. Question: Is there another problem that we are not correcting like a relay or something? Or just bad luck with wiper motors? I'd like to be sure the next one lasts more that a year. Thanks for your advice. Chuck in NH