I read on a previous post that you can re-use those refillable mugs to get cheap refills at US/IOA even years after you first bought them. I've got a Spongebob one that I bought last year - it is fairly long, blue with a built in handle and yellow lid in case anyone knows the one I mean!! If I took this with me on my forthcoming trip could I use it to get cheap refills? I don't want to try and be told no - my brother would KILL me for embarrassing him!!