Hi! I have a son who is 3 months old, but I also have an 18 year old daughter who slept all night at 6 weeks (from 6:30 p.m. to 7:00 a.m.) on her own. Bless her. Anyway, she did not require a lot of sleep during the day and by 9 months was only having really quick naps, if any at all during the day. She would be quiet for a little bit each day and that seemed to sustain her. I wouldn't worry and I think what we all need to remember here is that every child is an individual and although this is a great method, there needs to be some flexibility in it.
Good luck!!!