General question about FSB overvolting

When your OCing your current set up. When do you need? or would you ever need to overvolt your FSB?

i bumped mine to .01 but didnt notice anything different. Should i just put it back to where it belongs.

Essentially, you need it when it helps. if you don't notice a difference, it isn't helping and you might as well undo it.
I find that my e5200 needs it over 310fsb or so, but it only helps up to 1.26 or so, above that it hurts.

my mobo only allows 3 settings for the overvolting of fsb and i am stuck so i thought i might play with it.

353x8 e2140