Is it unethical to accept extra time on exams when I still do well? I have ADHD (real, diagnosed ADHD, not just "I-say-I-have-ADHD-because-it's-trendy" ADHD). I have never taken the extended time exams that are offered for ADHD students, because I have never needed to, and it was diagnosed just a year ago. However, exams do stress me out and I am certain I would do better on them with some more time - but this is true for almost anyone, not just ADHD students. Thus, would it be unethical to make use of the ADHD services offered to me?

(Edit: You might ask - why would you want to / feel it is justified? Well, hypothetically say ADHD students only achieve 75% of their "non-ADHD" potential in a standard-time setting. Maybe, even though I am doing well, I would be doing even better if I did have the extended time or didn't have ADHD, i.e. due to my exhaustive preparation, even with the disadvantage of my ADHD I am still managing to get a high score. But, with a "level playing field" [extended time for me], I would be at the top of the class. However, I still don't know if this is logical / ethical.)
Absolutely not. If you meet the full requirements set up by your University, it is perfectly ethical to use all of the resources made available to you. ADHD is a real medical condition and medical experts and policy makers have decided that special test accommodations are the fairest solution. Accommodations like this are based on medical decisions, not whether you are doing well in the course. Take the extra time if you want it. There is no need to feel guilty about doing so.