If you are only running a water pump, fridge, and detectors, plus LED lighting, a 2X 6V golf cart battery system in good condition will last 4-5 days. If you are boondocking, you are not likely to have over the air TV anyway. For entertainment, we read on an e-reader, surf the web, whatever, but that is done with portable devices that are easily charged in the tow vehicle (or toad for a class A.)
For microwave, hair dryer, coffee maker use, you will have to run the generator. For AC you will need the generator on all the time.