Quote from: Grinder on April 02, 2012, 01:40:22 PM

It's like speeding. It won't kill you every time, but it reduces the margin of error and increases your chance of crashing and dying.

Very good analogy.

To the OP once you find that speed where cards are stable for hours but not days then you are close but still "speeding" a little too much. Try dropping the clock 5-10 Mhz (remember every single GPU is different, there is no "standard" speed). Cards will likely now be stable for 72 hours+. At that point you need to decide if a reboot every 3 days is better/worse than dropping the cards another 5-10Mhz lower (where they may be stable for 30+ days).

Another thing to look for (in cgminer) is HW errors. Those are caused by the card returning garbage as "work completed". It is a good sign the GPU is redlining and is right on the edge of stability.

It isn't black or white. STABLE vs UNSTABLE. It is a gradient (hypothetical numbers):
Crash instantly (0.0 ms) - max speed
Crash in seconds - slightly lower
crash in minutes - slightly lower
crash in hours - slightly lower
crash in weeks - slightly lower
crash in months - slightly lower