Why pay $2-3 for a bag of cubed ice when you can make it at home for free? The cubes you make at home are usually more dense and they will last longer anyway. Plan out a few days ahead of time & start making ice in your own freezer before your camp trip. Stock up, it's almost free.
Freezing large water bottles at home is an excellent way to have "block ice" that last. Better yet, it doesn't sog down anything at the bottom of the cooler when it melts. Juice bottles work best.
Keep the sun off the cooler! Park this valuable portable frig in the shade all day when hanging at camp. If raccoons are present, you might need a big rock on top too. Taking the cooler out on a day trip sightseeing is a favorite option, cuz you'll have lunch time meals handy. When traveling in a vehicle, place a thick blanket or tarp over the ice chest. Even placing duffel bags on top will help save your ice on a long drive on a sunny day.