Is Taking Two Doses Of Vyvanse On Same Day Safe?

I am prescribed to 60 mg vyvanse and feel as though I may have a slight tolerance to it. I take it at 6:30 am on school days. it usually last me about 4-5 hours. I work in the evening and feel that vyvanse really helps me at work. would it be safe to take another 60 mg vyvanse at around 4:00 pm?