http://www.techradar.com/news/apples-jony-ive-reveals-iphone-x-was-in-development-for-5-years

The iPhone X has been refined to the point of perfection in the eyes of Apple, but it took a lot of failures to get there, according to its lead designer.

Apple Chief Design Officer Jony Ive, in a rare media appearance, revealed that the new iPhone was in development for half a decade – all the way back in 2013.