J.K.
Our first daughter was still waking up to nurse at night (around the same time every night) when she was 4 months old. At that point our pediatrician said that there was no medical reason for her to need to eat at that time and to break that habit. So, we let her cry it out. The first night I fed her after two hours of crying. The next night she stopped crying after two hours. The next night it got better and then she was sleeping through the night. We just had our third child and, I think it was at his one month well check (maybe the two week), we were told that since he had well surpassed his birth weight and was showing good signs of weight gain, that we didn't need to wake him up to feed him, just let him go as long as he would. He was sleeping 7-8 hours a night by 7 weeks old.