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.
U.S. cars from the 1950s to 1970s had an average life span of 100,000 miles, or eight years. Today, the median life expectancy of an American-made automobile is 12 years, or about 128,500 miles. While figures vary, the average life span of a Volvo is second only to a Mercedes.