To avoid excessive drying of the skin, facial masks shouldn't really be used more than once a week, which is the ideal. Think of masks like exercise - you won't get the benefits if you only use them every few months.

If you can't manage a weekly mask session, don't worry. The change of seasons at the end of summer (when skin is often thirsty after sun exposure) and at the end of winter (when skin is flat and dingy) are the two prime times to make an effort.