Massage is a very tiring treatment to give and hard on the joints and muscles. 4.5 hours is plenty if not too much if the client is very muscular or overweight. Both of these make it harder work.
I would book no more than 2 full body massages a day ( 3 hours ) to ensure that I aren't taxing my body too much. However I could add say another back massage or reflexology to the day. I am self employed and if you are the masseur yourself you would absolutely understand what I am saying. RSI starts at a very young age and leads to the therapist needing intense physiotherapy, rest from massage and wrist splints etc - I have been there and it quite frankly is not worth it.
Too late for me even with the use of elbows, forearms and wrist savers, which weren't introduced when I trained many years ago. Thumbs are ruined and my neck too. So ease up on the girls otherwise they will be off on the sick.
Introduce hot stones or make far more use of them. Get a G5 massager, Reflexology is an easier holistic treatment. Just put your thinking cap on and vary the menu a bit more. Hope that helps.