They will always die at the worst time, vehicle batteries, flashlight batteries, whatever.

It has always amazed me that car batteries will die completely with virtually no warning.

I have learned that here in the hot south, a battery in a large vehicle will rarely last longer than 36 months due to the amount of heat under the hood. It doesn't matter what the original warranty on the battery was. In a cooler climate I have heard that batteries might actually last until the end of their warranty. In our past 2 family vehicles I would watch the batteries and when they hit 36 months I would replace them. My wife now has a GMC Acadia with the battery in a compartment inside the vehicle, probably away from the hot underhood conditions and it might actually last longer. I'm not sure if I'm willing to risk this in the name of experimentation or just be conservative and replace the batteries as I always have. Before I learned the 36 month guideline I've been stranded in a lot of different places with a dead battery.