I have done no sleep training. I've lay down with all my kids to get then to sleep. Ds1 has slept through from 13 months and started going to sleep by himself around 3. Dd is completely different. She went to sleep by herself from around 6 months but still wakes up now at 3.5. She's had other issues though with multiple lots of grommets, tonsils and adenoids out etc and this has worked against her. Ds2 is 7 months and will sometimes go to sleep on his own but doesn't sleep through. I wouldn't expect him to sleep through at this stage even if I was sleep training though. So, I think all kids are different.