I toss any critical fastener previously used, be it engine, trans, rear end, suspension, braking system, a fastener can only survive just so many stretch, stress, along with heat cycles before failure...I generally prefer to increase the grade/tensile of the fastener if I can when replacing it
Absolutely spot-on...
That's what most people believe. Without any metallurgical background, of course...
Actually I have 35+ years experience in a metallurgical/engineering field