They (regular coolers) work pretty dang good in much warmer weather than Ya'll are talking. Its just that if your cooler has been hanging out in a garage in South Georgia in the summer or early fall when its 90 degrees, some of the ice you put in it before you head out is gonna melt getting IT cooled down. If you read the fine print on these ice retention tests/claims, they are for a pre chilled cooler.
I know when I would get a deer in South Carolina in September or October when it was still very hot, I'd get it on ice in a cooler asap and the ice had to overcome the residual body temp of the deer and the temp of the cooler. Half or more of it would melt overnight. After things cooled down, it would keep the ice and meat very well if kept in a shady spot. I would always check every day because I am OCD and some days did not require an ice top off even in mid 80 temps if kept in the shade.
The thing about my adventures is that they sadly don't take me far enough away from "civilization" to make ice retention a factor, nor are they frequent enough. There is a "twice the ice" machine around the corner from where I live where I can get 20lbs for 2 bucks. It would take me decades to make up the difference in ice saved by a Yeti vs a Coleman or whatever.
If it's going to be warm, use a 2d cooler for ice storage. Freeze a bunch of blocks and fill it up. Keep it covered with a sleeping bag and in the shade. You'll need to take an ice pick.
I've frozen a bunch of bread pans of ice and put them in small trash bags, 2 blocks/bag. That keeps them from freezing together and makes it easier to keep the food cooler topped off. Last summer, we took a scout troop to a week long regional camp out. We filled a cooler with ice blocks like this. By the end of the week, they hadn't even started to melt. We had plenty of ice.
