I take 210mg of Vyvanse (lisdexamfetamine) every morning per my doc. I tolerate this dose no problem, why does it worry ppl?

State of the art. Your doctor is practicing state of the art treatment for adhd. The practice standards specify using whatever dose is necessary to normalize function as long as its well tolerated. The actual number of milligrams is irrelevant. You tolerate that dose well so no problem as long as your adhd is fixed. Too many ppl are caught up in numbers without knowing the treatment paradigm correctly, ignore them.
Unusual Dose. The maximum recommended dose of Vyvanse (lisdexamfetamine) is 70mg per day. I personally have prescribed somewhat higher doses on rare occasions but nowhere near the dose you are taking. That is why people are concerned.
Vyvanse (lisdexamfetamine) Usually, max. Recommended daily dose is 70 mg. Taken once daily, however in adults who have high metabolism or who take medicines that lower efficacy of vyvanse, (lisdexamfetamine) dose can be higher, as long as they monitor their heart and liver functions. I have used daily doses of up to 180 mg., divided in 3 doses (am, noon & 4 pm. Advise consulting your pcp for workup.