I never really sterilized bottles (at any age). My kids both started getting a bottle from daddy at 3 weeks so they would take breastmilk when I went back to work. Maybe once a week I boiled breast pump parts and every month or so boiled bottles and parts. I don't have a dishwasher so wash everything in hot, soapy water. There is no need to sterilize on top of using a dishwasher, and generally hand-washing is going to be just fine.