I've never had to change my dosage of vyvanse for the past 4 years and have 0 withdrawal symptoms (I don't take them on the weekends or holidays, i've stopped f

I've never had to change my dosage of vyvanse for the past 4 years and have 0 withdrawal symptoms (I don't take them on the weekends or holidays, i've stopped for over 3 weeks before with 0 withdrawal symptoms).