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.
The Average Lifespan of a Desktop PC. With a desktop computer, you might see as little as three years or as many as eight, depending on the quality of the machine, how often you upgrade and how well you care for it. The longevity of a computer depends on the parts within -- and in a desktop computer, that's a good thing.