The treatment interval for the face/neck is every four weeks. The treatment interval for the body is every 6-8 weeks.
The recommended treatment interval is based on a scientific approximation that the hair will be in the anagen phase of hair growth on the face/neck every four weeks. Approximately every 6-8 weeks, the hair will be in the anagen phase of hair growth on the body. The laser only sees the hair that is in the anagen phase.