It's clear that he writes them the night before principle photography begins, granted he probably stays up all night, or most of it, in order to get the thing finished.
He has always been influenced in his writing by the memories of his youth, his passions and the process of working with far, FAR better storytellers.
But these days his influences are no longer so lofty as Campbell, Kurosawa and Buck Rogers and no longer so shrouded in the past.
All you have to do to see that is watch the two PT films.
Clearly while writing TPM GL was accidentally sitting on the TV remote and while shifting his butt back and forth on the computer chair he was clicking between C-SPAN and FOX Sports and some other channel where the Dinotopia book was being reviewed.
When it came to AOTC he must have had SpaceBalls on in the background.