Signing 'Milk'

I've been signing milk to Ty since he was a newborn.  I read that although babies don't have the fine motor skills to repeat the sign back, that they may understand and learn to communicate better.  So when Ty was 3 months old, I would say "Do you want some milk?" and I would open, close, open, close my fist.  By the time he was 5 months old, he responded to it.  Not all the time but I knew in his eyes, he knew that I was communicating with him. Now at 6 and a half months old, he will start getting fussy or turning around and mouthing my shirt and I will say to him "Tyler do you want some milk?" And he will usually respond with a big open mouth and put his mouth on my fist as to say "Yes! That's exactly what I want and I want it right now!"  Because after we have that little bit of communication, I cannot get him latched on fast enough.  It's all so wonderfully fantastic!