Unless you have two of the exact same computer 1 mining, and 1 not mining - its speculation. Its not a matter of the computer overheating, which none of my computers actually overheat - its a matter of shortening the lifespan of the CPU and GPU. If the lifespan when mining means that you need a new GPU a nd CPU every 2 years, whereas the lifespan not mining means you need it every 3 - although not ovverheating, you are still shortening the lifespan of the processor. Anything that runs hotter than 60 Celsius for extended periods of time risks the lifespan.