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.
You maybe working on an important project and your PC keeps shutting down randomly every 15 minutes or so. You hit the restart button and then it turns on again. Computer keeps shutting down is not a healthy sign. You need to carry out some simple diagnosis that helps treat the problem. Let us have a look at some of the causes that explains why your PC keeps shutting down randomly.