[JRL]

To be honest I used to think the same way about air conditioning but that was back in the days of manual air con. I would only turn it on when it was desperately needed and keep it off the rest of the time. In those days inefficient air con systems did use extra fuel but since I got my first car with auto climate control (Passat) and noticed no extra fuel use with it on I have my air con on all the time. Modern air con systems are extremely efficient and have a negligible effect on MPG. But they do have a huge effect on comfort and safety in my opinion. Keeping my windows clear and the interior of the car at a constant set temperature improves my driving experience no end.

As for wear and tear on the compressor? Turning the air con off and only using it occasionally would put more of a strain on the compressor than running it all the time. The whole air con system is designed to be in constant use. If running it caused wear and tear then we would all turn our fridges off at night before we go to bed and turn them on again in the morning.