I think a trickle charger/battery tender is supposed to increase the life, but I'm no expert. Most people with long winter seasons just take the battery out and keep it inside for the winter where it won't freeze. Before you start up in the spring, just throw it on a charger for an hour.
I have an 05 Ninja 250 and am terrified about having to sell it when I move for a new job. On the flip side, it may be the cheapest hobby while making no $. 130 bucks a year for insurance, 60 mpg and a few oil changes, not that bad.