How often do you change the feeding bottle?

At present, according to the material of the bottle, the bottle is divided into plastic, stainless steel and glass bottles. The shelf life of these three bottles is different. The first is the glass bottle, which can be used endlessly if it is not broken. Followed by stainless steel bottles, the shelf life is 8-10 years. The shortest is the plastic bottle, and the shelf life of the individual 3-5 years is over. However, the initiative here is to change the bottle whether it is outdated or not. Because the bottle has been used for a long time, it is easy to hide the dirt, and our daily clean and disinfection is actually no way to complete and clean. Naturally, no new bottle is clean.