As far as I know, there is no way to turn off the auto draft feature (I'm not referring to autosave or revisions).
I would like to suggest the auto drafts be visible in the list of posts in the admin section when logging into wordpress.
Instead of going to add a new post, especially since auto drafts are already there (but invisible unless looking in the database), being able to select the auto draft would enable the auto draft to become the new post. Each auto draft post needs its own title in order for it to be located for future edits.
I believe this change would prevent having "empty" auto drafts in the database by making use of them instead of cleaning them out after every 7 days.
Each auto draft creates a new ID number. WordPress should create ways to keep the post numbers at a minumum.