If you wanted to take this a little further, you could cover the "display" with heat erasable ink like is used in a Pilot Frixion pens.

This ink is interesting in that it fades when heated (60 C), but darkens when cooled (-10 C). In between those temperatures it is stable.

Thus you could have one loop that is continuously reused. Not sure how many cycles you can get before the ink degrades.