I do the same: I buy all my film in bulk (100+ rolls per order), and package each brick in a suitably-sized Zip-lock. I have yet to have any issues. My freezer to use time is one day (erring on the side of caution is my policy). Once removed from freezer to use I generally don't refreeze;the unused portion of the brick in moved to the refrigerator (not sure if this is necessary, but, once again, caution to avoid potential problems - real or imagined).