I've been on Vyvanse for years and it hasn't stopped working. If I don't take it, I'll feel tired by around 8 PM. If I do, I can stay up for much longer (alth

I've been on Vyvanse for years and it hasn't stopped working. If I don't take it, I'll feel tired by around 8 PM. If I do, I can stay up for much longer (although it doesn't seem to really hamper my ability to fall sleep).