When I plan out a project, I do calculate, “I need three days of poking at the project before I start.”
The reason is, I need some time between the completing of the beat board, and the writing. The story is cooking. Bits of dialogue are working. Scenes, visuals. Narrative.
Then I begin writing. I usually say, “okay, today I need to be at page 7.” I end up at page 4. Page 5 is good, actually, because I’m ahead of schedule when I get it. 7 is perfect. I can write a full two hour movie in 10 days at 7 pages a day.
Now, here’s where it gets interesting. As I write and get closer to the middle of the piece, my daily page count starts getting higher. 8 pages by midpoint.
9 pages by act 3.
10-11 pages when I’m doing the finale, because I’m getting excited, and enjoying it.
Just so you know, you build up a subconscious aversion to any project by the time you’re done with it, and it’s in filming stage – so I’ve been told. None of my projects ever got to actually “Day one”. I bet by the time they’re done filming it, the actors themselves feel like the screenwriter. 30-80 days of filming, and they’re sick of it.
By that time, the screenwriter’s got a year invested in it.