To be honest, I didn't believe that stimulants required daily use to be effective myself. Personal experience, however, has shown that they do. I find that I get the best results if I take my meds daily, it takes several days of taking my meds religiously to reach full efficacy, and missing doses or days seems to lead to a return of symptoms.
As far as addiction goes, it's unlikely that theraputic doses will lead to a serious addiction, though may indeed lead to a slight physical dependence leading to low grade headaches or fatigue upon cessation.