It's bulletproof.
Raising the clocks with Afterburner ( on a stock BIOS card ), closing it and re-opening it won't allow you to go any higher than you could go before.
Another reason to go for eVGA eLeet, no clock lims ( unless you think your card can do 2500MHz GPU Core clock that is
) and functional voltage control for most cards ( don't know if it works for the GTX 460, only tried it with the 480 ).
If it doesn't, I'd simply raise the voltage with Afterburner or Asus StupidDoctor and then overclock the card with eLeet.