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.
A PC may refer to any of the following: 1. Alternatively referred to as a Desktop and single-user computer, PC is short for Personal Computer and is a term coined by Ed Roberts when he introduced the MITS Altair 8800. PC is often used in the computer industry to describe an IBM or IBM-compatible computer even though the term PC can refer to any personal computer including an Apple Macintosh computer. The picture shows the Dell Precision 390 computer courtesy of Dell Inc. and an example of a Desktop PC.