That's a question there really is no good answer to. There are a lot of things that can lengthen or shorten a battery's life, including how often you ride the bike, what accessories you have installed, what tyoe of riding you do, what climat you live in, where the bike is parked, what season of the year if is, what brand battery you have...I've seen batteries last 1 year and die when the bike was parked over the winter, and I've seen them last over 5 years in bikes driven year round.