How often do I need to change my baby's milk bottles?

It depends on the material of the milk bottles. Most bottles in the market are made with polypropylene (PP) and these bottles should be changed every 5 to 6 months. Polyphenylsulfone (PPSU) bottles are honey tinted and sturdier. These bottles are naturally BPA free and can be changed yearly. Glass bottles don't need to be changed. http://www.totsworld.com.sg/what-type-of-milk-bottle-is-safe/