Just some observations. Our batteries seem on the small side for a 1100cc engine? At least compared to other machines & powersports. In general we ride in warmer weather than say a 4-stroke snowmobile with a battery.
Another generality is that those who use 'tenders' seem to get more life out their batteries? I use a tender on various machines, though periodically. It's not that it hurts to leave them plugged in, I just move mine around fairly often.
My main one is an Optimate 4, others are fine too.