There were four basic materials that the Egyptians used to build the pyramids: limestone, pink granite, basalt, and alabaster. Each type of material had a diverse use. Limestone had, for the most part, two uses.
To answer your question: The useful lifespan of a CPU is about 3-4 years. My guess on the technical lifespan under full load is closer to 8-10 years if nothing else breaks and takes the CPU with it. The reasons: High Performance Computing Clusters usually keep the computers for 3-4 years.
A new computer will also have some of the other hardware improvements from the last few years that will extend its life. There is always something new on the horizon but I expect the Windows 8 and Windows 10 computers youâve gotten in the last few years will last at least five years.