Run IBT with maximum RAM used if you don't have time or can't be bothered to wait.
Instability can cause chip degradation.
I agree with Justintime, if you're not stress-testing properly, why bother at all?
Some rigs can run for days stable and will crash at some point but the point of stress testing is to minimise the probability of having an unstable system.
IBT / Lynx is rubbish for Sandy Bridge. Prime Blend is the best test in my experience.