Electrical Problems?

[RastaGurl]

I had a similar episode this week: The car was left at the airport for 4 days while I was at a conference in Seattle, and I returned on Tuesday night to a dead battery. After waiting in sub-zero temperatures for about an hour, airport maintenance was able to jump start the car. However, it's taken a couple cranks for the engine to turn over yesterday, and it barely started this morning. I took it to the stealer today, who recharged the battery, and refused to replace it unless I paid for the replacement as, and this is almost a direct quote: "It's just fine, and as long as it's charged, is not replaceable under warranty." The SA suggested installation of some sort of battery charger which is permanently installed, and can be plugged in to charge the battery in the garage, for example. He also mentioned that I'd driven less than 2,000 miles in 3 months, and that probably had a bit to do with the inability to maintain a battery charge. I'm not quite sure I buy all this. Thoughts? Comments? Ideas? Should I just get a new battery even though they refuse to replace it?