Once every new moon
Funny how wishes are misinterpreted most of the time. When my aunt passed away, I inherited her wishing stone. I thought about wishing to be wealthy, or having the perfect girlfriend, you know, the usual stuff. I knew exactly how the stone worked. My aun had thought me well. I knew that for every wish I made for myself, I had to previously had made a wish for some one in need. She never told me what she had wished before, but I knew she had only used the stone once.