Yes I agree, routine 100% it definetly something that helps them know what is going on. The older they get the easier it is for them.

I have to admit I did a bit of Controled crying, my little man is 9 months and sleeps through perfectly. Since about 8 weeks. I only had trouble with day time sleeping. However the 'cues' are very important so whatever method you are introducing in your lifestyle try and stick to it for at least a month.

colleeg