How often do we need to change milk bottles (not teats)? My milk bottles have turned cloudy from the sterilisation, wondering if it is necessary to get new bottles.

To me... I make sure I change the milk bottle at least 6 months once..... my kids each of them have at least 3 milk bottles and I steam my bottles at least two times a day... eat h bottle used two times the max before each sterilisation.... after each wash I use hot water to wash before I place it back into the steriliser...