This needs to be determined according to the material of the bottle. If it is a glass bottle, it needs to be replaced with a new one or not for about one year, as long as it is disinfected with high-temperature boiling water regularly. If plastic bottles are used, their service life will be short and they need to be replaced in three or six months. If plastic bottles show signs of aging, they can also be replaced in advance. Generally speaking, breast-fed babies do not need special hydration before six months, and the frequency of changing bottles is from April to June.