https://www.cnbc.com/2017/09/20/a-999-iphone-could-spell-trouble-for-wireless-carriers.html

More and more, smartphone users are sticking with their aging devices until they croak, and the sky-high price tag for Apple's newly-unveiled iPhone X could accelerate that trend — to the chagrin of mobile carriers.

Over the past decade, mobile phone buyers have grown significantly more attached to their devices. The "replacement cycle" for wireless handsets ballooned to 24.9 months in 2016, more than half a year longer than it was in 2007, according to an August report from Recon Analytics. That's one reason why smartphone sales in general have declined precipitously in the past four years, to about 119 million in 2017 — down more than 9 million since 2014.