Pointless to ask, as it varies so greatly from woman to woman. Some insist on same day booking, others want more time, others book you and then ghost you on the very day of the session. The only semi-reliable bookings might be through the varoius spas.
Since I've started hobbying again in 2018, I've only ever booked a day in advance twice. Every other request was "hello....how soon can you see me, within the next x hours". There's no other way.