Sharonerd- it depends really on what electric kit you are looking at. At my shop, we encourage customers to invest in the more expensive and higher quality products that will and do last longer than lower quality lower priced products because they are simply made with better materials. The comments above that talk about 3 years on kit do tend to be the lower quality kit's life spans and even if you maintain them, the sad truth is that after 3 years, the company's reselling the lower quality product tend to not be around any more to enable you to invest in a new battery. Or the product itself has been sunseted and no spare parts are around. This can be true of the higher priced products too, but more so on the lower end.