My wife's iPhone 4S wasn't damaged per se, but after an IOS upgrade last year her battery life went from great to horrible. No matter what I did I was unable to remedy the problem from rebooting, to full system restore, to whatever. She was lucky to get an hour's life of battery before having to recharge her phone. It lasted for six months. Fortunately, she was eligible for an upgrade last month and I purchased the iPhone 6 for her. She hasn't put it down since!