how do you know if the bottle nipple is too fast?

My mom is on my case about switching ds to a 3m+ nipple, he was falling asleep at the bottle at 2m nipple and I didn't think that was a good thing. I'm using Avent bottles now, on 3m+ nipples and he seems to do fine on it.

My mom says she "feels" that its too fast

Am I missing some signs, how would you know its too fast?

Re: how do you know if the bottle nipple is too fast?

You can tell - DS would refuse the bottle because it was too fast for him.

Re: how do you know if the bottle nipple is too fast?

For DS, it would actually dribble down his chin and he was uncomfortable, you could see it was too much for him.