We started sleep training our tricky sleeper at four months. We managed to get her into her crib, but she screamed and screamed well past the four days we were promised it would take to get the job done. At five months, we hired a sleep consultant to help, which she did in certain ways but not in others. Months and months later, Opal was doing better, but still waking up at least once at night to nurse. In terms of nutrients, of course she didn’t need the night feeding still, but emotionally she still seemed unable to make it through without it. Three days before her first birthday, after a particularly bad sleep setback, we went for it and did another round of “cry it out.” It was so, so brutal but after a few days, she was sleeping through the night. She even started waking up a little later. So, Opal officially started sleeping through the night at exactly one year old.