It's a surprise. It looks like last year I made my reservation July 11. But they release the packages whenever they feel like it though I think there was a few days of advanced warning. There's a thread on here of people all watching and waiting to book, I suggest you follow that so you will know right away. Last year, some people did have luck calling when the bookings opened up and modifying their existing reservation (mainly it was for hard to get things like Garden Grill or Akershus) and adding the CP onto the reservation. So if there's a harder to get reservation that you want you can make it at your 180 and then try calling to modify when packages come out.