I can't see how doctors could possibly give you an a meaningful approximation to your questions "what is considered an average dose or what an incredibly high dose would be?"
40mg is recommended maximum dose of Adderall for ADHD. Psychiatrists do prescribe if necessary doses over 40mg; 60mg, 80mg, rarely more.
On the other end of dosing spectrum, as little as 5mg works wonders for some.
The average? Beats snot out of me.
IMHO, incredibly high doses are in excess of 100 mg/day.
Do not worry about tolerance at all. Given that the med continues to work well after three years of nearly continuous use, you may find a lower dose works just as well.
Don't worry. Be happy. Enjoy a functional brain. Nothing like a brain running within specs, eh? (My Canadian friends taught me "eh?" It so cool, eh? Damn, eh?)
Our advantage: People that haven't experienced brain bugs don't appreciate bugless brains. We do.
I forget how long for me - 7 or 8 years. I've been on doses between 10mg and 60mg. Currently prescribed 40. Sometimes I take less because I forget. I forget because I haven't taken the med yet. So how the hecks can I remember to take meds that enable me to remember? Huh? (Huh is eh translated into Jerseyish which is English screwed real good)