Park hours change question

When is latest you have seen a park hours change before your trip? Going May 2018 and hours aren’t out yet and I know they might change even after they come out but is there a certain time period (weeks, days?) that they are usually set for sure? Trying to do PPO breakfast at Be Our Guest and wondering if I should make the reservation on multiple days (since I don’t have breakfast plans on other days) to make sure we get a day with a 9am open

They can change at any time - during peak times they have even been changed the day before.

We booked a 8:15am BOG breakfast and 10:25am time as well. At the time we booked, MK was opening at 9:00am. They have now changed the hours to 8:00am so we are dropping the morning breakfast to take advantage of the lower crowds at park opening. We found that this system worked better than booking multiple 8:00amish reservations as every day our park hours changed to an early start.

Yep, they change all of the time. We are local AP holders and never know what to rely on.