08 Electra Glide, I got 6 yrs from mine. I only swapped it out because I could hear that it was starting to crank a little bit slower on a start up on a cold morning. I put another factory one in. After 6 yrs I was happy to try the same again.

From talking to people in GB , I'd say cool climate battery lasts longer. I had a genuine HD AGM battery last about 7 years on a kick start only Shovel Head. Never had it on a charger but road the bike all the time. Had original battery on 01 dyna last80,000k n 5 years. 

Had a new AGM battery go on me on the road once only few months old but had warranty they replaced it free that was 4 years back replacement AGM still going. I'll buy a new one soon as easier that stuffing regulateor alternator from runing a low battery