We booked all of our ADR's for our trip this past October back when there was only a 90-day window, and we usually shoot for around a 6 pm reservation. For a couple of the more popular restaurants (Le Cellier, Coral Reef, O'Hana) there seemed to be only 2 options - very early (4 pm) or late (8 pm). And this was at 6 am on the 90th day out! So the restaurant you want might have limited options, but I'm hoping it's gotten a little easier with the return of the 180-day booking window.