This may vary more than you know even to an individual. Things like caffeine intake or alcohol would have a significant effect on any person, young or old. IS OR VR is helpful but also my not be what you are asking about....I won't mention the "T" word.....
I am kind of curious as to why anyone would care what another shooter can shoot at handheld. I only care what I can shoot at, at any given scene. If some one can state that he can shoot a 500mm lens at 1/30 hypothetically speaking, what does that mean??? Does he have the same standards for sharpness as you do or me? What are his end uses of his images? How are his eyes functioning, and I don't mean he has poor eyesight, but does he interpret things the same way. Lots of factors enter in to this determination. My personal findings suggest I suggest I really need to use a tripod more, yes I used the word, I will go run and hide now....