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.
For monitors that are used 8 hours a day, an LED backlit LCD panel can last up to 25 years. Laptop batteries have the shortest working lifespan of any computer component. A typical laptop battery will provide 1-2 hours of run-time, and requires 2-4 hours for a full charge cycle. Typical Lithium-Ion laptop batteries are limited to 300-500 charge cycles, resulting in a lifetime run-time limit of 500-1000 hours.