I used to take Seroquel as well, so I'll chime in.

I would take it ~1/2 hr before I wanted to fall asleep. After that, I would allow for at least 9 hours of being asleep. I would also not plan to do anything requiring much cognitive functioning for at least 12 hours after taking it. The hangover can be a bear.

Also worthy of note is the fact that there is an inverse relationship to dosage vs. sedative effects. A 50-100 mg dose will usually be more sedating than a dose of 300mg+. I found this to be the strangest effect and very counterintuitive, but I know others on here have experienced the same thing. I was also informed by my doctor at the time that this could happen.

As always, your experience can vary.