I used to be one of the MOST vocal persons telling people that the mugs were not to be brought back on repeat visits. BUT, this last March when I was at the Boardwalk bakery the people working there insisted that the mugs were usable on repeat visits. I asked them if they were SURE, and they said, "Yes, you can bring them back as many times as you wish, and we will refill them year after year."
Keep me posted on this, because I don't want to pack that bulky mug to have it turned down.