I've been told not to do it, but when my daughter stopped getting full from the BIG size bottles but was still too young to eat by spoon, my pedi told me to do it so that she wouldn't start to lose weight. We never had any problems(use a fast flow nipple, do not EVER enlarge a hole yourself as it could causes pieces to break off and choke your baby!). I have heard that it supposedly confuses baby as to how to eat solids, but my daughter is already feeding herself w/ a spoon so I think that's just people being people. Now y that book says it won't keep them full longer is beyond me (don't u get more full if u eat solids and drink, not just drink?) but it probably will not make them sleep any longer. However, your daughter is 7 months old, there's no need to be putting cereal in her bottles- she should have been eating baby food and not just milk for months now! If she has any teeth, she's probably even ready to give her some finger foods, so if your baby isn't getting full enough on milk, it's b/c she's more than ready for real foods!