And when you do what size do you go for? Ds is 11 months and has 2 bottles of cm per day. I think we'll start giving him it in a cup shortly but atm do we have to change teats every month (I'm sure I heard this) and what size teats should he be using? He's also breastfed. He just had 4oz and he's got a size 2 teat (Avent) but it took him ages to drink what I consider to be a small amount- should we go up a size? Or does it really not matter?