I live in Chicago, where the winters are cold. I also travel a lot and my car gets parked outside, in the cold (occassional high temps of 0 deg. F) for up to 4 days or more at a time without starting up. How well do the Hybrid batteries seem to work during winter operations? I am considering a hybrid vehicle for my next purchase but am worried about battery life of the hybrid and perhaps serious degredation in gas mileage performance. Any experience out there with cold winters and the car parked outside for days on end without driving? Thanks.