I have iPhones for 10 years, and am currently on an iPhone 6s. My regret nearly 2 years ago, was that I didn't get the Plus model. I pay monthly for the phone and when I finish my 2 year contract, in Feb 18, I shall have paid just over £500, which is a lot less than the new model.
Unless I can get a new, bigger screen iPhone in Feb, for the same amount per month, I shall probably not bother renewing again.
I know that here is great rivalry amongst mobile phone users but I can honestly say that iPhones have never given me any trouble, and I can't see my self changing to any other make.