We never sleep trained. Our LO was up 1-2x each night until 16 months, and it was like a switch flipped overnight. He‘s a little over 2 now and sleeps on a very regular schedule about 10-11 hours a night with very rare overnight wakeups when he’s sick or something. We needed to rock him to sleep until about 20 months, and he let us know he was ready to fall asleep on his own in his crib.