Besides "pre-chilling" the fridge 12+ hours before departure, we generally put a frozen 1 gal. milk container (water...not milk) on an upper shelf when we leave. Without opening the door, that's maintained an adequate temp. for about 24 hours without power (and also provides really cold drinking water later on). Additionally, consider pre-freezing
any refrigerated items that can be frozen prior to departure, and putting as many of these as you can in the freezer compartment with the remainder in the lower compartment. I'm not necessarily against running with the propane on, just prefer to conserve the gas for hot showers.