K.M.
This may not be politically correct, but I rocked my daughter to sleep until she was around 18 months old. Partially because I was away from her all day and that was some of my evening with her. I may have just gotten lucky, but it only took a few nights letting her cry before she was going to bed with no problems. She was older and I think she could understand what was happening- that it was time to sleep. She sort of "got it". I say, do what works and if he is not able to go to sleep on his own yet, give him a few months and try again. There is no set rule for every child, in my opinion. Oh and she is now 6 and bedtime is not a problem, at all. It is good night and she is fine.