This is strictly my unprofessional opinion...I think your son is on too high a dose, and the undesirable effects are unlikely to go away if the dose is not changed.

I'm 40 and I take 70mg of Vyvanse a day for depression and fatigue. I've been on it for months and it is as strong as when I started it.

Not to be alarmist, but Vyvanse essentially IS speed--it breaks down into dextroamphetamine. I think it's a very good med, but it is pretty easy to take too much. But it may be a huge help to your son at a lower dose. Good luck!