dunno bout u guys, but im still on my original bat on my 04... tho it is ca and it does get ridden at least once a week.
if i had to replace it, know the cheap ass that i am, id find the cheapest battery that would work haha.
It would be intresting to see if i could disconnect the battery, and bump start the 919... might do that when this rain clears up.
also for you guys where its cold... and you wanna go start your bike up when its completely cold... turn the key on, and let it sit for 3 or 4 minutes with the headlight on. ... yes, let it sit not running with the headlight on. This will warm the battery up, exciting the chemistry of the battery and actually allow the battery to produce more voltage and cranking amps than if u just turned the key on and tried to start... this will also help produce a longer life out of the battery.