Look at the age-date on the battery. If it is not consistent with the manufacture date of your bike, I'd ask the dealer why. A new bike should be equipped with a new battery.
That said, lead acid batteries can and do fail, some earlier than later. Who knows, it may be a defective manufacturing problem or just an electro/chemical failure. Seems to me that you may just have bad luck on this. I suggest you ask the dealer for a little help here, and at least offer you a replacement at dealer net. That would seem like a good compromise.
'07 Kingpin Deluxe Tour
BrakeAway Cruise Control (the GREATEST!)