I don't really know how important it is to replace with a HD battery but my original HD battery lasted 5 1/2 years and I'll be the first to admitt that it didn't get an over abundance of attention. In the past on other bikes I've replaced batteries with supposed top of the line aftermarket batteries and did everything I could think of to take care of them and in 2 or 3 years had to replace them anyway. If 5 plus years is close to normal service life of a HD battery then I'll gladly pay a lttle more for one. Plus,you can just walk into you're dealer and get one off the self,don't have to worry about ordering and shipping and handling.