Pre-chilling a cooler buys you hours, maybe a day.

Probably a lot longer — hours to a full day, depending on the cooler and outside temp.

The logic is simple: ice melts slower when it’s fighting against a warm interior. If the inside of your cooler is 70°F when you dump in ice, that first bag is doing double duty — cooling down the walls and the air and keeping your drinks cold. Pre-chill that same cooler with a bag of ice or a few frozen water bottles for 12-24 hours, and the initial warmth is already gone. The new ice starts working on your food right away.

On a hot day with a good cooler (rotomolded, thick insulation), I’ve seen pre-chilling add about 12-18 hours. With a cheap soft-sided cooler, maybe 4-6. Either way, it’s the cheapest performance boost you can give a cooler. A bag of ice costs a few bucks. Do it.