The beauty of Ombre Powder Brows (OPB) is that they are very low maintenance. All you have to do after that is to shave/pluck/wax any brow hairs that grow outside of the frame of the brows.
Schedule a touch up once you see your brows are faded but still visible. If you need to apply makeup to darken your brows, you will already require a touch up session.
If you are unsure, send a picture of your healed brows to your artist for advice.