The hours are typically 9-5, and the cabana attendants have other assignments after 5. But one will usually be there before 9 setting up, and will be available for your needs.
As mentioned, the amenities seem to come and go. You can ask about something you would like but haven't seen, and they will do their best to get it for you, if available. The cabana attendants will take very good care of you.
If you are solo, don't worry about getting your money's worth. The Retreat service level is very high...