You don’t have to “Wean” off stimulant meds like you would with say anxiety meds. They are out of your system pretty much by the end of the day. Adderall IR should last 4 to 6 hours per dose. Talk with your doc. If the med is working for you, you are getting 12 to 18 hours of coverage which is a lot. You can very easily have a smaller dose at the last one. Heck, you can stop completely or just take one. The only effect will be that you will go back to normal ADHD behavior on the off time.