I wonder if this curve will change in a few hundred years. On one hand, people will have a lot more things to know than now. On the other hand, they will probably be cyborgs by then.
Actually the sweet spot is likely to move even younger as people can bypass many of the traditionally gating career points and get on with doing productive work at an earlier age.
Why wait for your Bio post-doc years and clawing your way up the Professorship ladder if you can do DIYBio in your kitchen?
Maybe this trend will be balanced a bit by the need to know more and more over time in order to reach a level where your research actually becomes novel.
More than a bit.
Much, much, much more.