When booking a few weeks ago for a Thanksgiving week trip, I went directly to Day 7 and had no problems getting what I wanted for a party of 4. A few minutes later, when booking FPs for our other Animal Kingdom day (Day 5), I could still have gotten a FOP, albeit with fewer time options. We didn't grab it, choosing to select Na'Vi instead (we are planning on rope dropping the other side of the park). In any event, somewhat surprisingly, for a very busy week, it was still available on Day 5 even after the window had been open for 15-20 minutes.