I freeze milk jugs then hit them with a hammer to break up the ice inside and then cut off the plastic and pour the ice in the cooler. This give's me small pieces to drop around the cans or food and larger pieces that last longer. I also switched to the extreme type cooler's and it helped alot. Another thing I do is cover the cooler with a moving blanket to keep the sun and wind off the cooler even when it's in the shade.