>the refresh cycle for PCs/Laptops is going to very soon be transitioning from the traditional 2-year cycle to 3-years, and, in the case of desktops, we're going to be seeing people run their systems for 4, even 5 years before considering upgrading.
We have been on a 3/5 cycle for the last 10 or so years. (3 year laptop/5year desktop)
We are likely moving to a 5/8 cycle with our current hardware.
> their dominant computer is their smart phone/phablet, which is being refreshed every two-years,
I am seeing less and less people willing to replace their phones on the 18-24 month cycle. The primary reason this occurred originally was cell phone carriers used the "upgrade" to lock people in to an additional 24mo contract. As we see less and less contracts and more people paying for their phones out of pocket or in installments, the replacement window is increasing, I expect by the end of 2017 to see the replacement be 36-48 mos for Cell Phones. This is especially true for any phone priced over ~$350.
Most of this comes down to how long the OEM will continue to issue OS Updates for the hardware, if your phone is getting updates to the OS 36mos after you bought it there is likely very little reason to spend another $400 on a phone. We will likely see some Manufacturers/Carries taking the opportunity to screw over their customers by refusing updates after 24 months in order to extort them into a replacement. Hopefully the market responds to these companies by pushing them to bankruptcy but...