It's so different for everyone. I was on 1200 mg plus a lot more sedatives up until February and couldn't sleep at all. I just adjusted very thoroughly to each dose so that it was not sedating. That's a very high dose used only b/c there were no other good options, but Seroquel worked for me when nothing else did for a very long time. I don't know how long it took to adjust to 300 because that was years ago but generally things got easier about 4-7 days into each dose.