@Teresa1505
1.) After booking: Thanks so much for booking . . . Lookout for a message with the important info like the check-in instructions and parking directions a few days before check-in . . .
2.) A few days before check-in: The important message with check-in info, etc.
3.) At some point during the stay: I hope you are settling in nicely and that you are comfortable. Please do reach out if you need anything at all.
4.) Around check out time: Thanks so much for staying . . . safe travels onward . . .
I think message #3 is really important. Of course, I do not demand a response and don't pry any further but I think it lets them know that I am available if needed and care about the quality of their stay.
It's like when a server at a restaurant comes back to ask you if need anything after you start eating. Everything is likely fine but it gives you an opportunity to possibly ask for more napkins, water, etc. If they serve the food and never return, many people would feel abandoned.