I must own the only two older iPhones that have not slowed down with age!!! Wifes 5S & my 6+ are both as fast as they were when purchased many moons back & both have less than 10% battery degradation even though they are charged every night without fail. Still get at least a full day without needing to charge out of both with plenty of screen on use (usually placed on charge with circa. 20% battery left). Both handsets are completely up to date with iOS updates as well.