For what it is worth, I spend anywhere from 2-8 weeks in a row on work related road trips and often park in one spot for well over a week, usually all backcountry. My wife who works remote for a major health care provider comes with me and can work from the road with our +55db cell booster. So I have 200W in two flex panels on the roof that feed the main large AGM battery, 100W removable slide out panel under the cabover and a 50W on the air damn which take care of the 75AH backup battery and my wife's computer.
I figure 350W is plenty for the needs we have. I turn the 12V fridge on this week, will leave it on 24/7 until sometime in October. I think the lowest I have ever seen either battery is 12.4V.
In the future, I dream of building a camper from the frame up that would have at least 600W and possibly 1KW so I could park an electric car next to the truck and charge it to whatever degree it would. I can't wait for the day this country pulls it's head out of it's rear and dumps burning oil...it's disgusting at this point that we still do it.