How do you know when to change teats?

[Sullwah]

My two boys are 15 weeks and are still on Dr Browns Level 1 teats.

How do you know when to move to Level 2's.

Level 2 is supposed to be from three months? Do I just change them or are there some signs I should be looking out for?

I never changed teats. I did try DS with level 2 around 3 mths, but he couldnt handly the flow, was too fast.

He has had no probs with level 1 throughout the whole year.

He was 1 on Saturday and I have just changed to level 2 now.