Good question, Rock.
Kinda depends on the position.
Some athletes are just freaks physically. Whitworth and Slater come to mind while playing a demanding position like OT.
Helpful rules changes are a factor.
Advanced nutrition and training are a big factor.
In some cases the obscene amounts of money are so enticing.
Some of these aging vets still love the game too much to walk away.
But I’ll say this. For some rare and freakish players it may well be the new normal to play until 40 or beyond for a few QB’s.
