I'm an editor. I advocate writing from your notes, not from your head. That way, seeing your notes tells you up-front how much material you have, and you'll gradually get to associate the note pile with the length of the article. (It depends a lot on the size of your handwriting.)
Plus, if your notes are rigorous, you'll have all your refs right there with them and will never have to hunt for the missing one ever again. That can save weeks!