It's completely normal for sebum production to resume after a week – that's just your skin's natural cycle. A HydraFacial deeply cleanses, but it doesn't change your oil production rate. The goal is to keep pores clear so they don't stretch out, not to stop oil entirely. To extend results, you should incorporate a gentle salicylic or niacinamide serum at home, and use a clay mask once a week to absorb excess oil. Also, avoid over-washing, as that can trigger more oil production. Going every 4 weeks is standard; going more often won't necessarily give you longer-lasting effects – it's about maintenance, not suppression.