What does time have to do with it? The insulation moderates the outside temperature reaching the contents, whether hot or cold. You would need to access and check the contents regularly anyway, as you would with most important pieces of gear or supplies. You can get a better cooler, with better insulation, or you can store in your car with no insulation, your choice. You pick which one is better. To insulate or to not insulate, that is the question.