They are not addictive at normal doses but there can be tolerance depending on your diet. This is actually pretty easy to treat - get a lot more magnesium and try NAC as well. (Vyvanse's effectiveness actually seriously depends on how acidic your diet is. If you take a dose with orange juice it may be completely inactivated.)
> Some talk about abusing alcohol to get to sleep.
Sleep issues (delayed sleep phase disorder) are themselves an ADHD symptom. If you time it right so the stimulant wears off at bedtime this can actually help you - but if it wears off early, I don't have the willpower left to go to bed.