I think it's good to leave your answers even if the OP updates h(er|is) post: (s)he clearly states that it's an update, so your post continues to make sense. OTOH, leaving messages is less worrying for you and added value for the community: people who's not fluent in English can read the same thing explained by two different persons (repetita iuvant, i.e. repetitions help). This can apply to English-fluent people in some cases too :)