For me, it was essential to walk my 7 month Grand Californian reservation. If I didn't I wouldn't have been able to book the room.
I was looking for a studio for 4 nights begining 8/19/15. Looking at the availability calender 7 months and a couple of weeks out I noticed that there was availability from about 10 days prior to what I wanted. I also noted that as the 7 month window opened the available rooms were booked quickly. Sometimes for just the date 7 months out and sometimes for two days. I decided to walk my reservation.
I was online at 8am trying to book a studio, but due to limited availability I failed to secure a reservation on 5 consecutive mornings. Finally, on my 6th try I was able to book 7 nights. I only had to walk a couple of days, then cancelled the 3 extra days that were at the beginning of the resv a couple of weeks later (I wanted 4 nights, not 7).
At any point guests whose home resort was the GC could have booked the available rooms and ruined my chances. But that didnt happen.
If I see availability disappearing at the 7 month mark, I walk the resv. I did it again for HH for August 2017.