Something to add: We purchased a new battery for another Porsche after 6 years, and felt that 28K miles and trickle charger were sufficient to keep battery charged. It was purchased from other than dealer, but was still expensive. Seller stated most warranties are dependent on use of the car, e.g. driving activitity, and that NOT driving car could be used as a reason NOT to support warranty, if that was determined. We never heard of such, but other than daily drivers may want to be aware. Do any of you have any experiences which support this attitude by battery manufacturers?