Many people book a throwaway room for just one night. They gain FP+ reservation privileges 60 days prior to check-in, and can make FP+'s for both the check-in and check-out day. You can continue to to make reservations for the rest of your offsite stay, on a rolling basis, one day at a time, 60 days out. The number of reservations is limited only to the number of days you have on your ticket(s).
For example, let's say I'm staying off-site for a fun Halloween treat from October 24-31 of this year. I book a throwaway room for the night of October 24th at All-Star Sports. Tomorrow, 8/25, I will be able to book FP+'s for October 24 and 25, my throwaway room check-in and check-out day, but not the rest of the week. On 8/27, I will be able to book for 10/26, on 8/28 for 10/27, etc., on a rolling basis for the length of my ticket.