So I started to give my son whole milk (he was formula fed) and now I’m wondering how it works? For example I know that formula had to be thrown away within 1 hour but what about milk? I do heat up the whole milk in a bottle warmer until it’s a little warm as I use to do with the formula but what if my son doesn’t finish it ? Do I throw it away or put it back in the fridge ? Ftm.