I wanted to add that I still take Seroquel both XR and IR, with no Seroquel hang over.
I have taken 600mg (and more) but never in one hit.
When my doses are high they are spread out over x5 per day. The earliest being 7-8 in the morning. The latest being 8pm.
Currently on a lower dose of 425mg prescribed and 100mg PRN (which I need 2-3 times per week).