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.
Best Answer: I have heard that you can comfortably keep PC's and laptops for about 3 - 4 years before upgrading. I guess it really depends on how well your laptop is currently running. If you are not happy with the speed and overall performance then it might be time to get another computer. Technology moves so quickly.