I have a 1995 Jeep Wrangler that I bought new; it had the original battery in it until last summer (2014).Batteries last until they die. I had a battery I left in a Chevy pickup for 8 years as an experiment. At that point I got tired of waiting for it to surprise me and replaced it one fall day before a cold spell. Another battery I put in my sister's truck lasted 1-1/2 years and worked fine until suddenly it would not start the truck. It failed internally with a open circuit.
Average life seems to be 4 to 5 years. A battery is relatively cheap and is certainly cheaper than a battery and a tow bill together, not to mention time lost and inconvenience.
I convinced myself that it was the best battery ever made, and then one day last summer all I got was click, click, click when I turned the key. Piece O crap battery.....