I just upgraded my computer’s CPU, motherboard, and memory. It has been a long time since my previous CPU upgrade – almost exactly 6 years. This is the longest that a CPU has ever lasted for me, and it was not top of the line when I bought it. It seems like the rate of performance increases has slowed down, at least in the desktop sector. I wouldn’t have needed to upgrade at all if it weren’t for doing a lot of compiling and wanting to play more modern games.
It seems like the mainstream software the most people use (OS, browser, Office, email) has not really put new demands on computer hardware. Some web pages have become more CPU intensive, but I feel like the hardware demands are limited by the prevalence of phones and tablets. With so many users having low end hardware (even top of the line phones and tablets are slow compared to desktop hardware), software requirements have stayed low.
Maybe once the mobile market has caught up we will see new software demanding better hardware. We should at least see higher resolution displays once the ultra-HD TVs start to arrive.