Well, my 3.8yr DS seems to buck the trend.
Lucky to get 11 hrs out of him, and thats often with one wake. No nap since 2yrs and a few weeks.
He occasionally will only do 10, but due to illness did 15 hrs overnight on Sat, and a 2 hr nap aswell!
Think its what he needs, as he wakes himself in the mornings - usually around 6, occasionally as late as 7.