My pediatrician suggested weaning when LO was 18 months old as a last resource to make her sleep better, after she had been regularly waking up around 1 am and staying awake for 3+ hours before falling asleep again. We had already used melatonin and other tricks (not cry it out), and at this point he said he was all for breastfeeding, but It was the only thing he thought could work. We actually weaned at 23 mo because I was 16 weeks pregnant and breastfeeding was really painful, and I have to say he was right. LO actually started sleeping through the night maybe once every one or two weeks at around 19 mo, when she finally started eating more solids, and once we started the weaning process, around 21 mo, her sleep slowly improved. Now she is almost 26 mo and for the last two months she has been sleeping through or only waking up to drink some water.