I know this isn't going to be extremely helpful but times when my son is super stimmy (at times he, too, could spend his entire day stimming) it was because something was making him ill. Once it was undetected metabolic issues, another time it was low iron and zinc, another time really high bacterial overgrowths, visual processing issues, and now parasites. Which sounds like he must be constantly like that given his age but when whatever it is was corrected each time he went back to minimal stims.
Given the stims your describing you might look into visual processing. My son had a great response to vision therapy and lost his visual stims.

 

just curious, what are visual stims? frequently when i read about others children's stims, i think, "oh, didn't know that was even a stim." i feel like i probably miss some of dd's stims, and i'd like to just be more aware.
also, rachelle, how did you know that your little guy was having medical issues (zinc, parasites, etc.)? when he starts stimming more, do you start looking at medical things? (also, sorry it's off-topic, i sent you a PM).
interested to see if anyone else has thoughts on this...