Not to say he's unproductive, because he's a beast, but I don't think he's a good example. Carmack got to work on really cool things which he loved (games) most of which were in his own company so he also had a stake on that.

Afterwards he had money to work on other stuff he was passionate about (rockets, VR, etc.) in his own terms.

It's much harder to draw motivation to meaningless work.