Is there a big difference between the Dr. Brown level 1 nipple (newborn-3 months) and the level 2 nipple (3+months)? When and *WHY* did you switch over, or did you just go straight to the level 3? FWIW, I use the bottles with breastmilk only, and the girls take over 30 minutes to finish their bottle of about 5 oz.

Re: Dr. Brown nipple flow ?
We switched to Level 2 around 2 months or so, mostly because it was taking them a long time to eat. We switched to Level 3 around 4 or 5 months, again, when things were slowing down. For DD who had thickened formula for her reflux, she had cross-cut Level 1s that were basically the equivalent of a Level 3. You'll know if it's too fast because they gag on it. If DS accidentally got one of DD"s bottles before we switched him to Level 3, he couldn't handle it. Same thing happened when we switched him to Level 4 around 7 months, thinking he wanted a faster nipple flow.
If your girls are taking that long, I'd try the Level 2s.
We switched b/c she was taking forever to feed... can't help w/ Dr B... we used born free but I can tell you there was a BIG difference w/ the level 3's ... it took DD a long time to get used to it.
I recommend just buying a couple level 2's and see how they do, then move up to a level 3 if you think they need it. DD would always choke at first, it took a few feedings or a couple days for her to get used to the new flow, you just have to keep at it. GL!