I didn't CC and Charlie eventually learnt to self settle at 11 months of age. It was a looooooong 11 months, don't get me wrong, and there were times I believed it would never happen. But it did.

I am not a believer in CCing in kids under 12 months of age, in that I would pick Charlie up if he cried. I then put him down when he stopped. I'd do this until he settled, and sometimes he didn't settle and that was alright too. But most times he would go off to bed awake and put himself to sleep. Charlie is now 2 and sometimes cries when he wakes in the middle of the night, but he can climb out of bed and come look for me if he really needs me (and has done so before when he's been sick) so now I don't go to him each time he cries.

I think before 8 months of age, when they learn object permanence, that leaving them to cry doesn't teach them anything about self-settling (because they don't understand that if you're not in their line of sight, that you still exist just out of sight). I think it teaches them that their needs will not always be met, which I think is quite distressing for the child at that age.

That's just my opinion though.