Unfortunately there is no guarantee that a replacement battery will last as long as your current one. I've owned batteries that lasted six years, and others that barely lasted one year. The brand name on the label seems to have little to do with longevity (the one I owned that barely lasted one year was from H-D). I'd suggest saving some money and looking at the batteries from sources other than Harley. I've used Deka batteries, both those with their own name on them as well as the same item from Battery Mart that has their name on it. Work just as well as the H-D labeled part, for about $50 less. If you want higher cranking amps, try the Yuasa (Japanese name but made in the USA). They are more expensive than Deka, but still less than H-D.
JMHO - Jerry