I don't really understand why, if you escort full-time, you wouldn't take same day bookings? I can understand a bit more not showing your phone number, but a lot of punters will not be interested in emailing, so no number displayed, no business from them.
I'm low volume, partly as I do another job from home. So long as I have anything from 30 minutes (if I'm already showered) to an hour (if I need to shower, do hair and make-up) to get ready I'm fine with it, as I can usually just put my other work to one side for an hour or two.
I'd say 80-90 percent of my bookings are same day, and most probably booked no more than three hours in advance.
You do of course get timewasters on the phone, but I think an advantage is that you can tell virtually straight away that they're either a TW or someone you have no interest in seeing, so perhaps in the long-run it saves time wasted on emails (or texts).