This is from the FP+ FAQ sticky thread:
For purposes of this thread, a “split stay” is defined as two (or more) stays scheduled back-to-back where the checkout date of one stay is the same as the check-in date of the next stay.
Despite some changes to MDX in early 2019 regarding split stays, the system has settled into a new “normal”:
- As before, for multiple back-to-back onsite stays at Disney-owned resorts (or any resorts that qualify for the 60-day advance window) the booking window will open 60 days before the check-in date of the first stay and extend until the checkout date of the last stay.
- If offsite stays are combined with onsite stays, no benefits of the onsite stay will apply to the offsite stay. This is a change from prior behavior, especially when an offsite stay follows an onsite stay. In this case, the 60-day “rolling window” no longer occurs, and FPs for the offsite stay will not open until 30 days before each day in the offsite stay.