B.F.
I changed nipples a month later or I went by the way they where acting all kids are different I think the listed on the nipples are a guideline you don't have to be right on to the date. As far as burping when my kids ate table food and no longer took a bottle as a baby like I guess up until about 12 months old or so. It's kind of a live and learn situation with each child. My best wishes to you.