At times I have had a supply of canned or bottled food and/or produce stored in my plastic cooking bin or canvas zip bag. I dutifully cook and very much enjoy the results. But cooling the leftovers is a problem. I’m on my third Styrofoam cooler. One lasted five days. The second lasted one day before cracking and leaking. The third is faring better since I no longer store my laptop next to it, but ice is $2 a here and often it melts without me noticing.
I threw out the leftover fried potato and burger/purple cabbage/tomato fry I’d made when I realized the melted ice was no longer cold. Such a waste.
Living in a house I would always cook enough food for leftovers. I did not and do not like to cook, so making more than one meal at a time was a strategy for eating well. But living out of a portable cooler, who knows if ice bags really keep meat leftovers at a healthy temperature, even before the ice melts. The temperature varies depending on whether the food is above or below the ice, touching the ice bag or a layer away, etc.
I shopped online for a fridge/freezer that runs off car batteries. There are great options made for truckers and some for car campers. But they are several hundred dollars and take up a lot of room. Solar would be better yet, but yet again more expensive.
In both cases, I would not want to leave an expensive item like that at the campsite, and I have no room in the car for it. Even if I could fit it during the day, it would be heavy to lift them into the car during the day for security and to the ground at night to make room for sleeping.