And BTW (been wondering), has your son inherited in whole or part your blessing of only needing around 4 hours sleep/night?

(N.b. I was interested reading recently in the NYTimes about a famous athlete who attributes his success to sleeping a lot - often twelve hours a night.)

I guess there have to be people at both ends of every distribution.

short-sleeping seem to be genetic

That athlete:

Justin Verlander, "sleep guru"