Can you try this test if you have: ORBX FTX PNW scenery, PMDG 737NGX, REX E+, and an nVidia card?

I know this is against the conventional wisdom, but I have a different take on the whole issue of evaluating system stability by running the multicore routines that arguably stress your system more than FSX does.  I know heat generation is any indication, temp definitely goes up significantly w/ Prime95 over what it does w/ FSX in my build.  JJ at Asus in his video re overclocking SB-E mentions this issue and I think it makes pretty good sense.  Why not set up the machine to run FSX as the burn in routine?  If the logic holds true you should end up w/ lower voltages & temps to get FSX to run stable compared to what might be required for these synthetic benchmarks to maintain stability.

Precisely!

At last someone has said it.

Stress testing utilities like Prime95, Aida etc. are very useful, but that's not why we build our machines. We certainly do not build our computers to run Prime 95 all day with stability... on the contrary, we build our computers to run FSX [and any other software we regularly use] with stability all day.

The true test as to whether your system is stable is how well it runs the software it was built to run.

You could go on and on and on, with ever more stressful stress tests, ad infinitum. So your system is stable in IBT, great news, then some smart programmer comes along with an even more stressful test and it fails... what then? Do we mess about with the voltage even more, tweak even more? No, of course we don't.

I run Prime for an hour or two, and perhaps Aida64. That's it. I then run my system while keeping a watchful eye on it. If it blue screens, I would make a note of the error and act accordingly, increasing voltage if required. So far, it's not been necessary to do that.

Why run at voltages that are required for many hours of a particularly vicious stress test, but not at all required for the software you built your machine for in the first place?

It's also worth remembering that stress tests often don't keep up with CPU architecture developments. You may find yourself running a version of Prime, or IBT, that isn't validated for your CPU. And then you scratch your head, wondering why it keeps failing and temps are through the roof.