Hopefully you’re having this conversation with your doctor as well. Everyone is different, and there isn’t a standard dosage/treatment plan that works across the board. Through trial and error is how you find what works for you.
That said, there are things that work more often than others. Personally, it seems to me that “take when needed” doesn’t work well for most people. At least not from what I’ve read and observed, which is not exactly scientifically valid information. But if you’re concerned about addiction and abuse, an unpredictable med schedule is more likely to produce that result than a predictable one.
I have a friend who also has ADHD, and he takes medication only on work days. He doesn’t seem to notice that his ADHD is not well controlled, especially when interacting with his family on those non-med days (it’s complete chaos for everyone).
I take my meds every day, and while I haven’t achieved what I would consider optimal treatment yet, I’m still way ahead in having symptoms under control in all areas of life compared to my friend. Again, this is just one little example, and everyone is different.