You will get answers for both sides but I book when I know my dates are set or close to set and then wait for discounts to be released. I have had my May and Sept reservations since May of 03.
I found it easier to change a room-only to a discount faster then doing a new reservation when discounts are released. Think of how many people are calling at the same time and if you take 2 minutes instead of 6 or 7 minutes that means two more people can get their discount too.
I like to think of everyone else too. I never call for PS dining at 7 am because everyone is calling for CRT and I want Chef Mickeys.
Lori