A Burger King processes on average $1500$ customers$/$day $($over the course of $14$ h$).$ At any given time, $40$ customers are in the store. Customers may be waiting to place an order, placing an order, waiting for the order to be ready, eating, and so on at any given time, there are $40$ customers in the store. How often can the manager of the store expect that the entire group of $40$ customers would be entirely replaced$(40$ new customers are in the store$)?$