1986 Toyota MR2 repeated A/C compressor failures

Has become a chronic problem with this car. I'm on my 4th compressor in the last 6 years. Aftermarket or rebuilt makes no difference. 3 years ago I had the system completely rebuilt- new compressor, condenser, evaporator/drier, expansion valve, plumbing; lasted about 15 months and quit cooling. Last one was also good for about 15 months, and it's gone too. Question: What could be the underlying problem here that causes this car to eat a/c compressors on a regular basis? Otherwise, a great, very reliable car. Thanks a lot. Hoping you can help.