I was JUST gonna post the same question. My DD just turned 6 months but I still lurk on here! I started her on Medium flow a few days ago and still use slow flow through out the day. She is doing well with the medium...spits up a bit more....but so far so good.
We switched to medium flow just before 3 months. She was getting frustrated with slow flow so we knew she was ready. It has been great, because it only takes her 10-15 minutes to down a bottle. It used to be more like 30-40 minutes. No increase in spit-up or gas for us.
We use Avent...we were on a 1 until about 5 weeks & have been on a 2 ever since. I just tried a 3 the other day b/c DS was getting super fussy when eating.
I think DS was probably about 10 weeks. It was taking forever to finish a bottle. Now it only takes 10-15 min. He didn't catch on right away, and a lot of the bottle was coming out of his mouth, but after about a week he got the hang of it.
Re: slow flow to medium flow nipples
We use Avent...we were on a 1 until about 5 weeks & have been on a 2 ever since. I just tried a 3 the other day b/c DS was getting super fussy when eating.