An EPS box has no fixed number of uses; the test is that reused packaging is easy to clean and, where necessary, to disinfect (EU 852/2004, Annex II, Chapter X, point 4). The box has to pass that test again on every return.
A broken corner opens a heat path and stops the box above from seating. Deep scratches and holes make cleaning harder, and a box whose lid no longer fits does not insulate. So five points are checked on every return: are the corners intact, does the lid seat fully, are there deep scratches or holes, is the box dry, is the inside clean and free of odour. If any answer is no, the box does not go out on the next trip.
