It varies from person to person, but I generally recommend getting it every 4 weeks. Of course, there are individual differences depending on the speed and amount of hair growth, but if more than 5 weeks pass, you may experience discomfort as the hair grows significantly. You must be especially careful during your period, as the risk of bacterial infection is high. Therefore, for hygiene reasons, it is recommended to get a re-treatment within 2 to 3 months.