Depends for me if within a month or two it starts to be cloudy, dirty Ill change. Throw, buy new ones. Therefore, I will always have atleast 5 bottles to interchange when needed.
I sterilised after each use too. I change the bottles when baby reaches 4 months and to a “bigger” teats when the old ones had bigger holes and affected the milk flow.
Thks!!
itsallabout_mytwokids