The place where I work is closed for about three weeks at Christmas. Last year, my Mustang sat for a good part of that time - including some comparatively cold temperatures (it's under a free-standing 'carport' type structure, so the sides are open) and, when I returned to work, it fired right up as if it hadn't been sitting, at all.
However, I have been driving my Bronco II for the past couple of weeks due to periodic heavy rains, some flash flooding, and the simple fact that I want to keep miles off my Mustang. After sitting for about three days this time, my battery was dead. Recharged it, drove it and everything was fine. Let it sit three more days - dead battery again. I did notice, however, that there were a couple of wires on the amp for my subs that were loose and thought I might be getting a slow drain from something associated with that, so last night I redid those connections and put the charger on the battery again. We'll see how it does this time. While connecting the charger, I noticed that the battery is a Motorcraft. Isn't that what Ford puts in at the factory? If so, I guess that there is a good chance that it is the original battery that was put in the car roughly five years ago (bought the car used last year, so I can't be sure).
Your car is newer than mine, and an S197, and mine is a GT, but maybe this will help give some perspective. Good luck!
Oh, you might want to have your battery checked by someone other than Ford. The Advance Auto in the town where I live puts the battery on a machine that checks it to make sure it can hold a charge. It takes about twenty minutes and the bonus is that it also rapid-charges the battery as part of the process. I haven't done that with the battery from my Mustang, but I have with other vehicles. They have never charged me anything for this service, even if the battery turned out to be 'good' and I wasn't going to be buying anything from them at the time. I don't know if doing that would have any impact on your warranty, though.
__________________ 2002 GT, 5 speed, Zinc Yellow
BBK CAI, Flowmaster cat-back
The secret to a happy ending is knowing when to roll the credits - Drive-by Truckers lyric
Some say, "The enemy of my enemy is my friend." It is wise to remember, though, that sometimes the enemy of your enemy hates your guts, too. - Me. | 
