The [Wordplayer](http://wordplayer.com) site has a [good anecdote](http://www.wordplayer.com/forums/scriptsarc05/index.cgi?read=40628) about why it’s important for screenwriters to stay active throughout production:
I’m on the set less than a minute and I see Miss Improvise, in costume, her makeup being touched up, all ready for the first master shot.
She’s supposed to be dead. Dead for at least twenty pages.
Definitely worth a read. Check it out [here](http://www.wordplayer.com/forums/scriptsarc05/index.cgi?read=40628).