My milk dried up when I was around 3 months pregnant - at least I think it did. That was the time when DS stopped wanting to feed to sleep like he always had and I couldn't squeeze anything out myself. DS kept dry-feeding for a month or two, but eventually he stopped wanting it and had fully weaned by 22 month (2 months short of my goal). I'm sure it is different for everyone though - perhaps the younger the child the more likely they'll keep going because they feel they need it more?