When you overclock your video card, how do you know your video card can run safely and effectively at the overclocked settings? How long does it take for you to become confident that your system is stable?

I have an Asus V7100. It's a GF2 MX. My motherboard is an Abit BE-6 v.1. It doesn't have the 4x AGP speed: only 2x.

I'm using the Asus Tweak utility to overclock the Video Card. The engine speed is at 185 MHz (I can't be set any higher) and the memory speed is at 175 Mhz. The defaults are 175/166.