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.
So WiFi web browsing battery life, arguably the most common user activity there is on a computer these days, goes from 4.7 hours on the Surface Pro to 6.7 hours on the Surface Pro 2, a 42% increase.