I updated my top choice with my new shadowing hours because they specifically asked me in the interview why I hadn't shadowed in several months (summer classes, DAT etc...). I don't think its that big of a deal if you've already interviewed and you want to show your continued interest in the field and their school. If it's schools you haven't even interviewed at I would only do it if your application was deficient in some way or if you have significant new hours in something. No plans, just what you've done.