My Dad is currently on the iPhone 4s running iOS 7 (managed to stop him from going to iOS 9 which from experience is terrible on the 4s) and I've finally convinced him it's time to upgrade. He doesn't want to spend a lot of money on a new phone as he doesn't upgrade very often. He had the iPhone 4 from 2010 to the start of 2016 and then he inherited my Mum's iPhone 4s, so you can see he doesn't upgrade very often. Is the 5s still a good buy? Bearing in mind that by his count, he's going to keeping this at least three years, will it still be good in three years time?