I observe that many people have issues with their new iPhone 6, which is to be expected unfortunately from a massive launch of brand new hardware. I've also seen news articles and posts advising people to sell their current devices shortly before a new launch in order to recoup maximum value. I think this advice may be mistaken. If you have a device that works and is stable, I think it makes more sense to keep the old device until the new one is confirmed to also be satisfactory and stable. I keep my old phone as a spare. If N is the current generation phone I bought, I keep my N-1 phone as a spare. N-2 generation sold or donated. Obviously this strategy may or may not be appropriate depending on individual finances.