Auto Draft

I am a bit confused over post_status auto-draft. It is used when storing you location amongst other things. If you insert an auto-draft but then don’t over write it you can end up with 100’s of unwanted auto-draft records in the database. How do you get rid of them? When I was googling I found something that said they were automatically deleted every 24 hours. Is that right or do you have to use wp-optimize. Thanks