I'm really not sure how that follows at all. If the battery life of a new device is 3 days, and the battery life of a 2-year-old device is 1 day, at no point i

I'm really not sure how that follows at all. If the battery life of a new device is 3 days, and the battery life of a 2-year-old device is 1 day, at no point is there battery power that is unused.