A lot of iPhone users have been complaining about there battery issues before iOS 10 was released so Apple thought of slowing down iPhones when iOS 11 was released this only majorly affected iPhone 6s some people have claimed the iPhone 6 works much faster than the iPhone 6s Apple did admit to it as older the devices get the batteries need replaced every 2 years because of daily use instead of replacing every 2 years they try to increase the battery life by decreasing the speed on earlier iPhones