How much will overclocking shorten CPU life?

[dsmartuk]

I have a I7 920 D0 and Gigabyte ex58-ud5 and it came pre overclocked to 4.0ghz 191 x 21. I've updated my bios and am now able to achieve higher speeds i.e. 4.2ghz (200x21)

I was just wondering by how much am I shortening the life of the CPU by running it this high, and what is a sensible speed to have this board and CPU overclocked to?

Many thanks

 

[DIABLO]

You're only really shortening it if you run extreme volts and/or run it hot. I've always overlocked my CPU's and have never had one die.