(aside, the forum has recently different rules, not letting me edit posts after a while)
I was going to edit to say the Everfrost is risk mitigation, it mitigates the risk you are away from civilisation for many days with a need to keep things cold. But those risks are also mitigated with assuming the Everfrost fails either due to itself or what powers it. So I’d recommend to enjoy it’s benefits but have a habit of placement of it and how it is packed with an assumption it will fail or power to it fails. Keep in shade, lower down, etc.
You what assumption did? It assumed itself correct.
Physics: the energy input (warming) to it is to the square power (surface area) but the temperature (energy density) is to the cube power (volume).
So if you’re not space constrained, and if you’re on a long remote trip, best to buy the physically biggest Everfrost (which increase energy input to square) but fill it with dense products (water is a good choice) so it’s temperature raising is reduced to the cube.
However if you wanted to minimise energy use, so a shorter trip, you’re using it off it’s internal battery only, then buy the physically smallest as less surface area, the pump has less work to do.
Combined will make those who buy an Everfrost get the maximum benefits in more contexts.