I am planning on starting cereal with my lo today. I am going to mix it with formula to get him used to the taste in case I have to supplement when I go back to work. I was planning on using the little bottles that the hospital gives you. I have never used formula before. How long does it last in the fridge once it is opened? Any thoughts on mixing cereal with formula? My lo is 6 months old and EBF. Thanks in advance!!