What are the warning signs?

[al bundy]

I currently have a non-overclocked Ti4600 card with the Zalman ZM80A-HP cooling it passively (as in the sig). Zalman says this fanless cooler should provide adequate cooling for this card, but they also then say that a slow fan blowing over it "would provide even better cooling".

This cooler gets mighty hot on both sides, especially during a game - but I never see any artifacts or image problems. I have two exhaust fans and one intake fan moving air through the rig.

So, does this mean everything is really OK? What are the warning signs if a non-overclocked card is getting too hot?

I'm hoping that I would see something that would warn me of overheating, instead of the card just suddenly dying(!)