Hi, my son uses the NUK bottle and teats. The HV has told me to change to the next teat size so that he gets his milk easier and doesnt get tired as much. My only worry is that the next teat size is 6 to 12 months, he is 8 weeks and the teats he uses is 0 to 6 months. Has anyone else had to change the teat size too early? and did it work?