My kids hardly ever change doses,  my oldest was on the same dose for years-  we lowered for about a year to have his growth catch up a bit,  but raised it again, he was really out of gas on the lower dose.  My youngest rarely changes his dose either.  Maybe a minor change, but it does go up and down, not just an increase because they are older or bigger.

My kids are still on a fairly low dose.  The 6 year old takes 7.5mgs (total) and my 9 year old takes 10mgs (total).  I am going to the Endo next week so we will see how they are doing.