Overclocking had a negative effect. If the overclock not go stable, the computer will go hang, BSOD (Blue Screen On Display), can’t boot. But its just a little problem. You can clear CMOS and the CPU will boot again in default setting.
But how about the worst in overclocking?? Your cpu will overheat, and maybe will broke permanent because the temp too high.
In theory, overclock can decrease the age of prossesor. That was designed to remain approximately about 10 years. But in 10 years, are you sure didn’t want to replace the processor with the new one? are you sure at the time your processor could be still being used for the application in the future?
Technology changed very fast, and i was sure you will not use the processor in the next 10 years, and why didn’t try overclock then?
And decrease the age of processor just in theory for me, because the new processor has designed to control the temp of processor. If the temp exceed, it will be shutdown and goes to default setting. the other ways, you can find the better cooling for reduce your temp. Many cooling for this time, from the normal Heatsink Fan ( HSF ), Watercooling, until Liquid Nitrogen (for the extreem overclockers )