I've never done longer than one day trips, so I haven't paid much attention to the quality of coolers. For me size was important but keeping time no so much. I was also doubtful about whether there's really a difference between a marine cooler and a regular cooler. Anyways I had some people over Sunday and put two bags of ice in the cooler. Afterwards I left the ice in the cooler to see how long it will last. It's been 3.5 days and after emptying the water there's still the equivalent of one bag of ice left in the cooler. I remember someone told me that it's good for 5 days. So I guess I recommend this cooler, it's an Igloo 128qt. Another thing worth mentioning is that it was used/old when I bought it, so there's little if any deterioration due to only time.
I may run the same test with my coleman cooler which is around 80qt and not marine grade.