I bought a battery Tender Lith Ion battery for my previous bike, and it was giving me 4+ years and going strong before I traded in the bike. It has been claimed that a Li Ion battery will last 7 years, and for a bike, that's very good. I think I would have gotten at least that longevity, had I not traded in the bike.
Dale, that's how I tended my Li ion. If you get a Li Ion, follow Dale's post above. Also, in my research I found advice that says you should use a Battery Tender charger for a Battery Tender Li Ion battery, or even for a non-BT Li Ion battery. It seems the Li Ion has different characteristics that don't lend themselves to continuous trickle charging. Maybe some experts will have posts to explain this.
Steve's post above is also good to consider.
But, JimmyK, it seems that you are very good at maintaining your normal battery, and economy-wise, you might do better financially with a normal battery with your current trickle charger. Five years on a MC battery is much more than what is expected, with or without your limited riding times. Some folks who don't ride much tend to neglect the battery in their machines. Even a good new battery becomes insulted with neglect. I've seen them last as little as one year without maintenance.