AnthonyGA:
Think back to that Colgan Air crash. The pilots were young indeed, and perhaps they had cat-like reflexes in consequence; but they made all the wrong decisions, and so, instead of rapidly getting out of trouble, they rapidly got deeper into it. Would a 65-year-old pilot with thousands of hours of experience in similar situations have made the same wrong decisions? Would he have even allowed himself to get into trouble to begin with?
Stupidity, lack of skills and/or training know no age or hours...
Think of Crossair BAe 146 crash in 2001...
Captain 56 y/o with 20000 hours and yet managed to fly a VOR approach without adjusting V/S as the speed was reduced. Resulting in the path gradually becoming steeper and steeper until CFIT 3 nm short of runway. Not to mention a bunch of other mistakes, such as going below minimum without runway in sight. The final report is scary read, as it goes into great detail about the commanders history. Impressive that he managed to stay alive for such a long career. Maybe he got away unharmed from the incidents the report mentions in the past because he had not yet fallen below your "100 threshold" of acceptable performance mentioned in one of your post a couple of pages back.
Some may hack it at old age, some not. Better to make a cut-off so no one slips through. Too much "buddy-buddy friendliness" keeping people in the business already, that should have been hauled out. The only effective regulation for keeping the bad old ones away is to keep everyone away.