My YETI Tundra is an ice chest that can keep ice (not even dry ice, that would be longer) for over a week. On one of my tests it was almost two weeks. They are used by campers, river runners, fishermen & -women, field camp workers, anyone who needs to be able to count on their cooler to do it's job. I've only had my YETI for about 8 years, but have always had good ice chests. I keep it covered with insulated bubblepack or a canvas tarp, and throw an insulated sleeping bag over the top of it; so even a less efficient cooler will keep ice longer using that method.
The YETI, when padlocked, is bear-proof: "The YETI Tundra® and Roadie® meet the Interagency Grizzly Bear Committee (IGBC) standards for bear-resistant containers when used with extra-long shank Master locks. Our hard coolers have been thoroughly tested in both controlled bear simulations and with wild grizzly bears. When padlocks are used properly, grizzlies get nothing but frustrated after coming across your cooler."
It was inspired by the process of roto-molded plastic used for kayaks. When padlocked, bears just cannot get a claw-hold on it. Not that I will participate in that testing but it's good to know! The ice chests I grew up with and until relatively recently, could not be sat or stood on as it would damage the seals. This thing is indestructible. I even use it for grocery shopping since we live away from town. I use it for pretty much everything but backpacking :-)