just like CPU OCing, we need to run a maximum load on the GPU.
playing a game for a few hrs is not it!
for me, i run 3dmark11 10 consecutive passes, then Heaven 10 consecutive passes, followed by 8 HOURS of OCCT with 0 errors. And of course, no driver crashes.
this is a STABLE overclock.
what i see others posting cannot possibly be.
granted gpu's are like cpu's in that no two will ever overclock the same.
i have a gtx460 reference card
max OC is 900/1800/2100 @ 1.0625V
i have had this card @ 930/1.0875V, but OCCT gave errors, so it was not stable.
seeing others claiming to have a stable OC of 990 makes me wonder what their definition of stability really is...
You are right, some guys will post incredibly high numbers, but that was only because they could get the computer to boot up, the system is still unusable. Others find a card that is more stable at higher clocks, some use more advanced cooling gear such as phase change systems(simular to AC cooling) or some use photoshop and cheat.