Its hit or miss with ford factory batteries. I replace them all the time at my work and the motorcrafts I put in don't last that much longer either. Heat is the number one killer of them, especially down here in florida. Take for instance the Lincoln LS, the battery is in the trunk. I have been a ford tech for over 6 years and I can count on one hand for the batteries I have replaced in a LS(not counting batteries dieing from draws or alternator failure).