It may vary, if you use a lot of make up and you are exposed to sunlight pretty often, once a month can be appropriate, if not, every quarter should be fine, ask your dermatologist, if you have very delicate skin, you can help yourself taking care of your skin at home every night, use hypoallergenic products to clean it before you go to bed, drink lots of water and eat lots of fruit, specially apples and grapes :)