How far in advance can I make FastPass+ selections?
If you have a Disney-operated Walt Disney World resort reservation, you can make FastPass+ selections starting at 60 days from your check-in date, up through the length of your reservation (including check-out day), for as many days as your ticket length. If you have tickets that are longer than your reservation, you can then continue you make additional FastPass+ selections 60 days from the date in question, up until your check-in date arrives. At that point, you cannot make selections beyond the 60th day from the check-in date, until you get to 30 days away as a non-resort guest as explained below.
To clarify by way of example, if your check-in date is July 1st and is for 5 days/4 nights (check out on July 5th), and you have a 10-day Magic Your Way ticket with No Expiration, you can begin making FastPass+ reservations on May 2nd, and can make FP+ selections for July 1st through the 5th (5 days worth). You still have five days left on your ticket (perhaps you are staying off-site later), so on May 7th you can book FastPass+ for July 6th (60 days from that date), and on May 8th you can boot July 7th, etc. As long as you have less days of FastPass+ booked than your ticket length, you can do this up until July 1st comes around, when you can book August 30th but you cant book beyond August 30th at all until you get to August 2nd, at which point you can book August 31st, and follow the 30 day rule from then.