Hadn't ever heard it called "controlled crying" before. It looks like this is also called "self-soothing". From reading the first few articles on a google sea

Hadn't ever heard it called "controlled crying" before. It looks like this is also called "self-soothing". From reading the first few articles on a google search of the topic, this looks very similar in nature to the Baby-wise technique of establishing a routine which will cause the child to settle into a nighttime routine and let them sleep through the night. Why wait until the child is 6 months old? I didn't see any reasons given on the (admittedly few) articles I read. Children crave routine, and ISTM that the best time to establish one is as soon as the parents are ready for it.