I think it depends on the type of session and the interplay between the MPA and the client. If it was a NR and oil was used, then I think most ladies tend to soap up, rinse and free up the shower to the guy.
The shifts are 8-10 hours long. That could mean as many as 16 sessions per day for the busy ones. You cannot expect them to shower after every single session. Some may wash up and use a face cloth or baby wipe as opposed to that many showers.