Because of all the false beliefs and negative opinions about stimulants, medical professionals will often cater to it rather than fight it. And, of course, just because someone is a doctor doesn’t mean they aren’t prone to misunderstandings that lead to false beliefs themselves. Find a new doctor if you don’t trust the one you have.
Some people do outgrow ADHD by early adulthood, but they are the exception to the rule. Medication doesn’t cure ADHD, it only treats it for as long as you take it. Just as glasses only treat poor eyesight when worn.
Your treatment needs may change over time, however, so it might be useful to take break and slowly reintroduce medication starting with a low dose and working it up to effectiveness. But that should only be done when your life can handle some temporary increased ADHD symptoms. And it should only be done under the guidance and advice of a doctor.
It has been shown that eating healthy and getting enough sleep are very important for maintaining medication effectiveness. Talk with your doctor about diet and sleep if you think it might be a concern. Also, cognitive therapy is known to be a very effective companion to medication, and is strongly suggested by the FDA as part of the first-line treatment of stimulant medication.