For me it was about 2 weeks of euphoria when I first started. But I also made the mistake of drinking a coffee with it back then, which resulted in major euphoria with a horrible crash inbound for the evening. (1-2 Coffees 8 hours after intake is fine for me though.
I‘m not a doctor and YMMV.
I can only speak of Vyvanse, but generally I have to agree with what you describe. Yes, stimulants are addicting and have potential for abuse, but so does sugar, caffeine and nicotine.
But if the meds work as intended, they will also keep you more lucid in your decision making, which lets you have more control over your behavior. Short: Treat the meds like e.g. sugar or caffeine, stay at a constant dose, tweak it slowly and do some breaks in between to check your dependence and reset tolerance.
Coffee withdrawal headache is soo bad.
All I‘m saying is, you might not need to quit it entirely. Just reducing it based off the reason that it‘s not a good stimulant for treating ADHD.
Right now I‘m really happy with my 4pm coffee, work‘s done by then, Vyvanse wearing off and a mental down / headache / tiredness creeping in…BOOM: Chief Crema comes barging in and saves the day.