My go-to masseur allows a half hour between appointments so that customer one has enough time to shower if he wants to, dress, make small talk, etc. before customer two shows up. All he asks is that you message him if you need to use the shower before hand; and then he usually asks you to be early so that the actual massage starts on time. Massages are for the full time booked whether you shower or not. That break also gives him time to answer phone messages, change linens, and relax for a bit. Seems like a good business practice to me. And in several years I've never run into another of his clients.