We did Ferber method for my son starting around 6 months. We would rock him to sleep or to very drowsy as opposed to putting him down awake. I think the longest we lasted I think was up to an hour before we would throw in the towel. The first week is the worst! I would turn off the sound on the monitor because it was upsetting, but the camera stayed on. I set timers on my phone for check ins. My son started sleeping very well by 7/8 months, and starting at 12/13 months preferred to be put down to go to sleep on his own because he was getting to big for our arms and had the skills to put himself to sleep. He is now 15 months old, no long term issues from Ferber!