The best thing my psych told me is a mental disorder is only a disorder if it gets in the way of you living a quality life. You not feeling the need /want for a larger dose means its effective and you're consistent in taking it. I've been on my current dosage for a while now and don't really feel the need to up it, and that's fine with me. A lot of ADHD meds are amphetamines and the less you can take the better probably. I'm possibly having to deal with high blood pressure as a side effect and that's no fun.
TL;DR listen to your body and if it's saying your good then your probably good. Do talk with your psych about it though.