I am storing them in the fridge wrapped in clingfilm and they seem OK so far, but I'll let you know.
Recipie is 2 egg whites whisked until light and airy, mixed with 90g sweetner and whisked well. Then put in oven at 130C for 1 hour. Turn oven off and leave merguines in there until totally cool (I leave them in overnight) so they go crispy all the way through.
They dont taste as good as real merguine, but I mix them into yogurt and fruit and can't tell the difference then.