I keep my battery on a Battery Tender whenever it's parked. Some may feel that's overkill, but my battery has been in my bike since February 2002 and has never let me down. Your battery should be fine, just keep it on the Battery Tender.
I do the same. Got my bike in early 2005, it's on the tender pretty much anytime it's in the garage. I had the 10k done on it earlier this year (yes I don't get to ride as much as I wish!) and I had them check the battery level as it was 3 years old, and they said it was almost fully charged.
How you ride affects battery life too though. If you tend to do short rides (under 10 miles) then you'll drain it faster. Longer rides help keep it fully charged. Makes sense when you think about it, when you look at how much juice is drained each time you start a bike.