The cpu has to be stable in all test Period!. Chances are I would never push my cpu to those extreme limits but who the heck knows?
If the OC can handle 90c cpu load from LinX, i'm already in the right direction to a stable overclock. Since some CPU fail after higher temps even if they are stable at lower.
It does not have to be stable in all tests. That's just stupid. I am never going to use AVX2 applications, so does that mean I need to be Prime 28.1 stable? Nope. I'll be just fine with x264 and my gaming/encoding.