I am always amazed how people think they need to book in advance. We have been on 60 Princess cruises and have never ever had any issue with getting into the venues on the same day we decide to eat there. I have never seen any of the venues full after 7:30 or 8:00. We generally look at the dinner menu in the morning and if there is nothing that hits our fancy we get a reservation through the dine line. They never book every table in advance