Jung, Campbell, and company never addressed what happens after the Hero returns with the boon.

Indy has already brought the boon home, he's crossed the threshold, he's the master of the two worlds. (TLC.) Theoretically his story is over, his hero story.

But what happens next? Just because your hero tale has been told doesn't mean it's over.

Of course it stands to reason that he had more adventures and experiences--it's true to his character. But it's obvious in TKotCS that he's continued to hold onto these revelations--the illumination he received in TLC. It's the cycle of life--the hero continues to move on and returns as the sage. And he has to pass the knowledge on to someone else.

Sorry--I know I'm rambling here. I'm just gaining illumination.