You guys talking about clear block ice with no air and cooler management and getting 16 days should try parking your truck in the Arizona desert for five days when temps hit 128F and there is no shade and your big ice chest is servicing about eight adult males and a couple of kids. Maybe I could find clear block ice, but it's 30 miles to the nearest gas station and 50 miles to the nearest thing that can pass for a town and about 75 miles to the nearest place with block ice. As to the ice to drink ratio, I'd rather buy ice when I can find it than run out of drinks in East BFE.
While moving
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Here's your shade
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Whenever I can, I freeze the drinks before I pack them into the cooler, but once that load turns back to liquid, it's a constant fight to keep it cold.