I've had a mixed bag with my three. In answer to your question, my second son slept through from 3 weeks (his lead and in hindsight I wish I realised how lucky I was). I used to dreamfeed him around 10pm ish each night. As for the others, DS1 slept through from approx 3 months of age, and we're still waiting for DS3 to sleep through, but I think he likes boob too much as he generally grizzles till he gets a bf in the wee hours. He always starts the night off in his cot, and ends up in our bed at some stage, so we're co-sleepers by default