There is another pool of data (a little more extensive) on frontal lobe maturation in children diagnosed with ADHD, which finds that they are about 3-4 years behind NT children. Anecdotally, I do find that functional improvements follow a similar pattern. In my adolescent students, quite often children with EF delays appear to have EF skills "kick in" in the latter half of high school (just as their long-suffering parents were about to despair!). I conceptualize this as the difference between having the EF skills of an 11-year-old (elementary school equivalent) when you begin high school, and thus being way out of your depth with regard to managing multiple classes, long-term assignments, and independence, and having the EF skills of a 14-year-old (high school equivalent), and thus being able to handle those demands, despite ongoing delays.
It's not exactly that their ADHD resolves, but that EF becomes good enough. These are kids who may always be a little scattered, and should definitely aim to become so successful that they can hire a personal assistant, but at some point, they often reach the point where it's not an obstacle anymore. Then there are others who actually appear to normalize, but very late (like in their 30s).
http://www.nimh.nih.gov/news/scienc...in-adhd-but-follows-normal-pattern.shtml(The link above has some nifty animations. Your kids, in particular, might enjoy seeing what happens in the brain during development. Note: the animations are in color, which some research has suggested is more convincing to cognitive neuroscientists than black-and-white brain imaging. Really.)
