I have the Igloo Kool Mate, but they are all pretty much the same idea. My best suggestion is to just prechill everything that's going in and if you are taking meat or such that you are not using the first day then freeze it first before putting it in the cooler. Not only will that help it survive an extra day or so, but it will act like a block of ice and help keep things cool. Basically, if everything is well chilled to begin with you can probably let it sit 3 or 4 hours, but not much longer than that. They are insulated, just not nearly as well as something like the 5 day Xtreme ice coolers or the like.

If you are just doing one or two day trips you should be fine. I was fine with mine for short trips too unless it was super hot outside. It was my week in Eastern Oregon last August while it was 85 plus outside with no tree cover that really got me thinking about a better solution.