I've been taking 70 mg Vyvanse for years. It generally works well. Although there are occasional days where I feel like maybe it's not quite as effective as it should be. That probably has more to do with outside stressors and diet than anything. By this point I've built up some tolerance to it. I know a lot of other people try to take breaks from their stimulus occasionally to try to help with the tolerance.
Well, I've learned that that is not for me. I tried taking breaks two Saturdays in a row and holy shit, the anvil-on-chest anxiety is more than I can take. Feelings of dread that I have not felt in years come bubbling right back to the surface.
This is something that I have, in the past, tried to explain to parents who are apprehensive about putting their kids on stimulants. For me, the worst part about ADHD isn't the poor short-term memory, it isn't the inattentiveness, It isn't even the "inner restlessness". It's the emotional dysregulation. The fact that it makes me feel anxious and depressed all the time and I can't just shrug it off. It's like a dark cloud hanging over you and no matter how much you wish it would go away, it never does. And, if you don't want your kid to kill themselves or develop substance abuse issues, then you need to try to help them get a handle on it while you can.
It took me 28 years and becoming a borderline alcoholic to get the help that I needed. I guess if I didn't get anything else out of my experiment, I got a reminder to not take what I have for granted. Getting my meds dialed in dramatically improved my quality of life.