Whenever I get the "what time are you free" questions I simply reply "please tell me when you would like to visit me and I will let you know if that is possible" and if no follow up from them they are ignored from then on. Doesn't matter if they send more messages/emails, I don't reply. Ping pong messages are of no interest to me at all. Everything they need to know is right there where they found me, my flipping profile.