Over clocking always increases processor temperature and it will diminish cpu and cpu fan lifespan. Now, If you want to over clock; it is necessary to increase the Core multiplier, the voltage and any other BIOS settings is automatic.
I recommend you to install our software Intel® Extreme Tuning Utility. Intel® XTU is a simple Windows*-based performance tuning software for novice and experienced enthusiasts to overclock.
Why is CPU life time diminished? I overclocked my older Nvidia 9600 GT and also GTX 570 years ago by 150-200 MHz (and 570 even increased voltages) and they are still working (not in my system anymore, but they kept working until I replaced them by newer one)
Will CPU life time be diminished by the heat only (only temperature reason? And why high temp so bad?) or also by the fact that higher frequencies run through the nanometer structures? What is the reason for decreased life time?