I'm no expert, but I've had a National Luna fridge running for two years (nonstop). Mostly in the house as a beer cooler. It does have a freezer, but my understanding is that the "freezer" is simply kept 20º F lower than the regular storage area by directing more freon towards the freezer portion. The temp is determined by the "fridge" part...not the "freezer" part.
In short, I simply plug my fridge into 12V when I leave and I move to the house (on 120V) when I return. Always on. I've read that there is an esoteric situation where the fridge temp can drop below your set level (and the fridge turns off) which leads to the freezer getting warmer (because there is no call to cool from the internal thermostat). This can theoretically lead to a situation where you fridge in not running and your freezer is no longer freezing.
I live in Montana and have yet to find that my frozen stuff is...well...no longer frozen. I wouldn't worry about it dude. Set your fridge temp, plug it into your rig, and go camping!
If your fridge doesn't have a freezer, then just plug it in and run it forever. If it doesn't need power, then it won't use any.