There are some R12 units out there since 1989 still running smoothly. Our first year return rate is less than 1% and we are constantly striving to improve it. Unfortunately, environment plays a big part and if a unit is placed in an unacceptable location, life cycles can diminish rapidly.
Similarly, dirty (chicken feathers), greasy (restaurants), dusty or acetic locations can spell trouble. Uninsulated cement floors are problems as is the mildly acetic atmosphere in some wine cellars which can corrode refrigeration coils.
To compound the problem the new (R134A environmentally friendly post 1995) refrigerants are not at all like R12. Remember that fridge that lasted fifteen years. The new R134A has an affinity for paraffin's and carbon compounds and that, simply put, leads to "hardening of the arteries". In addition it is aggressively corrosive to the metallic and other compounds in the compressor.
This is the big secret that most manufacturers just don't talk about and also why they also hesitate to repair sealed systems. Repairs on R134A units are risky. Once the unit loses it's charge, it becomes contaminated and manufacturers generally prefer to replace the sealed system rather than brazing the leaks and recharging the units.
We will not repair a sealed system that has a leak. We will replace the unit instead. It is the only completely reliable way of fixing the problem.