My mum said that I used to do that as well and my LO takes like 20 to 30 mins. Have you tried to offer more? If they take more they are still hungry, if not, well, I would imagine you have yourself one efficient eater on your hands. Well done. I WISH harvie would take 10 to 15 mins!!! I have to fight with him to take his normal 160mls in 30 mins...