In all of my WDW trips I have ALWAYS booked after the discounts are available, usually 2-6 months prior to the trip, unless it's a bounceback.
I select resort and room based on what has a discount. Works great!
For example, booked our March-April 2019 trip in October, after discounts came out.
Booked our May and July 2019 trips in January, when AP rates came out.
Planning at least one trip after SWGE opens, sometime between September and December. Haven't booked it yet because discounts are not out and I don't know what will work best with discounts