While I don't know the specifics of your setup, just 3 days should be a piece of cake if your house batteries are in good shape. We don't have a motorhome (shopping now) we do have a 5th Wheel and regularly dry camp for up to two weeks at a time.
We run our fridge and furnace as needed, and additionally RUN the DirecTV receiver, the TV, and my wife's bi-pap at night via an inverter. Most of my lights are still incandescent. It's never been a problem. I just top off the batteries in the morning and again in tne evening by running the gennie.