Just my 2 cents worth. I grew up with a Camper DeVille, a short lived manufacture in Hot Springs Ar, made in the 60s, like an Apachie, but heavier aluminum that opened to one side, anyway, it had a built in cooler, it was about 20 inches deep, 40/42 inches wide and 22/24 inches deep. It was made of tin and 2" of insulation, it was built in to the trailer and the top was plywood with 2" of insulation & metal that inside the inner walls.
We would put dry ice in it before a trip. Probably 5o lbs. It sayed cool for 8 and 10 days! My parents use to rent them in a little camper business and someone rented a trailer and went through Az desert heat and they used dry ice and said it lasted for almost a week.
We did not drain much of the water out. The water was ice cold and kept items cold enough. My mom would put jugs of drinking water in milk cartons. The trick is keeping the ice chest full of items, as we used up food, it was replaced with more food or we put additional milk cartons full of water in there. Another thing is that we used plastic (tupperware) containers keeping items dry. We used a smaller cooler for my drinks as a kid I was always getting into it, so that limited the big coller being opened, but not like we didn't use it. Keeping a coller or ref. or a freezer full of something makes it work less. I keepwater in milk jugs in the freezer in the garage to keepit from running all the time....it's just a big ice box. Keeps dead space out and items stay cooler.
I will be looking for a new cooler soon, I have been using plastic cheap ones for the boat forthe afternoon. I see the refrigerators posted here for $600 and up and seems nuts to me, since I think of that old built in coller in the Deville. I have not tried buying dry ice lately, so I don't know if you can even get it anymore, but if it is still readily available, I'll be going that route without power drains, break downs and limited storage space. Now, if I were in a motorhome, that's different.
