I went to St. Louis office today to get my passport stamped. The lady told me if I need to change my address I am better off just going back to their office and do it there rather than sending address change form to NSC. Her explanation was, they process address changes the next day and they get to the system right away, while it takes NSC quite sometime to do the same thing. I am sure she wasn't marketing their service, she was just being informative.
Good luck
Good luck