It is technically 180, but they are not always bookable at 180. The times for the shows need to be posted before they post the DPs for booking. Happens a lot with both dining packages and dessert parties.
I was surprised, but A friend decided to go with me next month, I had the Tomorrowland Terrace dessert party booked (on a non MVMCP night) and they were able to add him to the reservation just over a month out.
The Feb booking for the Star Wars dessert party didn't open until Nov. They often don't open 180 days out. Depending on the time of the year they don't necessarily sell out either.