Ya, you don't want to jump out the low refrigerant sensor unless you're in the process of filling the system. If it'* not jumpered out then the system will never accept any more freon. If you're not filling the system, it'* a good way to smoke the compressor!
Back in my real cheap days, I used to unplug the power lead to the compressor so that it wouldn't kick on with the defroster. It was one less accessory being used that would help me save gas. Think about it...cars without a/c (my Cheby p/u for ie) will defrost just fine without the compressor kicking on.