This Computerworld article is about PC and server hardware lasting longer and how the reason for replacement of even machines of advanced age is often driven by software needs, rather than failures of aging hardware.
One thing it doesn't say is that even older computers have the capacity to do many worker's jobs without either benefit of new software or hardware upgrades. How much computer does one need to do word processing? This is the other factor that makes Microsoft's job of selling upgrades to Office so difficult and why they want to switch their basic revenue model to subscription or rental instead of one-time sales. If both the hardware and the software do the jobs at hand, why buy newer stuff?