Just had one go out today. Bought it in the spring of 2012. I always took it out in winter, threw it on charge once a month and install it in April. Same holds true for three others, I average 4-6 years. I have a 6v in my old Ford 9N tractor, it was bought in 2009 cranks and starts fine, same routine. Don't let them run dry, buy fresh ones and keep them charged in the winter.