DARN TOUGH STICKERS! Dishwasher, rain, mud and adventure proof stickers!
The night before you leave throw some ice in your cooler to pre-cool it. That way when you put your ice block in (highly recommended over loose ice, most grocery stores and large gas stations sell them) it's already cooled down from being in storage. Put your ice block on the bottom and fill the cooler as much as possible with your stuff. You want as little space (air) as possible. This will add days to your cooler's life span!