The refrigerant (what you are calling "Freon") is captured inside a hermetically sealed fluid circuit. The capacitor, on the other hand, is an electrical device and doesn't do anything to the refrigerant directly. It helps the compressor and condenser fan start and run.
The refrigerant isn't the problem, and if you've replaced the capacitor more than twice it probably isn't the caps either. I suspect you have a power quality problem or some loading issue that is causing your capacitors to fail.
M's comment on moisture in the refrigerant isn't wrong. If you're getting some fly-by-night tech to charge up your system or, God help you, doing it yourself, you may have introduced some moisture into your refrigerant and that's killing your compressor. The first symptom will be the caps dying, but the compressor is going to go next if that's the case.