There is nothing wrong booking in advance it all depends on the girl. I regularly book a week or more in advance as I know my schedule ahead of time, why should i wait and risk the time and the girl I want get booked. If I suddenly have an emergency that I will need to change my schedule I can always ask her politely to change the time.
But then it depends on the girl, some would gladly take booking in advance, some would reply asking you to wait until closer to the date, some will just ignore you as they are only focusing on bookings on the same day or the next day or two.