6mo DS is mix fed (2 bottles a day on top of BF on demand). We're still using the same slow flow Tommee Tippee teats we bought when he was born. Should I be replacing them with faster flow teats? He seems perfectly content with them. I think I have slow let down and he sometimes gets frustrated on the breast so I am worried if he gets used to faster flow bottles he will start refusing BFs. Should I just stick to what works?