We advise to change the bag every 3 days, of course this depends on the odour of the diapers. When your baby only drinks milk the odour is less intense versus a baby who eats meat and vegetables. In summer when the temperature is rising it's necessary to change the bag more often. We also advise to 'air' the pail of the DiaperChamp once a week (outside) because odour can be sticked to the plastic.