That used to be the case, actually life cycles in earlier years were sometimes even shorter than that (apparently it was only a year and a half back in 2007 -- http://reconanalytics.com/2015/02/2014-us-mobile-phone-sales...).

But several articles seem to point out that the upgrade cycle is slowing down -- up to 2 and 3/4 years according to this source (https://www.npd.com/wps/portal/npd/us/news/press-releases/20...) for instance.

I think the second link is correct that 5G might offer some incentive to upgrade, but else wise there's just less reason to constantly upgrade your phones these days. The delta between an iPhone 7 and an iPhone 8 is not that huge versus the delta between an iPhone 3GS and an iPhone 4.

Yes, maturing technologies seem to have longer life cycles. It's the same thing that happened with PCs. Compare the life cycle of a PC made in 1990 compared to one made in 2015.

Americans are a small percentage of the world market, and Americans buying flagship smartphones an even smaller percentage of that market. Of course people with a lot of money can afford to upgrade more often. On HN we tend to forget that not everyone is so lucky, both in terms of job market and in terms of disposable income.

I'm assuming that at some point, there will be very few new features to get people to upgrade. I think we're already seeing a slowdown.