The most important factor in predicting compressor failure can be found by the cleanliness of the Oil.
Virgin oil is clean, nonconductive and the primary insulator against voltage leakage to ground.
Equipment manufacturers for the most part put together very clean systems and when properly maintained can last a long time. Service technicians do their part by taking all the right steps when opening systems for repair. But despite every precautionary measure taken by the manufacturer and service company, changes in the oil can occur beyond our control. These compounds will be found dissolved in the Oil Phase. The protection one would assume from driers is limited.