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.
Well, according to the CIA's The World Factbook, the current average human lifespan is approximately 66 and a half years. On average the current life expectancy for the world is about 67.2 years. (see the first related link). The current average life expectancy for just the US is 78.3 years.