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.
When we buy cheap laptops, how long does a laptop battery last? Battery life of such laptops are not as good as the high-end laptops. The estimated average battery life of the continuously used laptop is around 3.5 to 4 hours and this short period is mainly due to the modern graphic-intensive operating systems and applications. Tips to Improve Average Laptop Battery Life