Will it ruin the A/C system sooner if I leave it on all the time, when turning off and starting the car? I heard that it can ruin the compressor if it's left on and the engine is turned off. I just want to know if that's true. Because of that, I always turn the system off when turning the car off.

__________________
1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500