Steiner talked about the beginnings of the emergence of the "I" at about 3 years of age. This is seen by the child referring to herself as "I", usually for the first time as well as the emergence of the memory and the first whispers of separation of the child from the mother. The Madonna's Cloak now fades away.
Other than that, one can take Steiner's powerful picture of the tiny child being wholly open to the universe and being like a sponge in terms of sense impressions to judge what might be right and healthy for her. And one major piece that he talked about - and which I bang on about at regular intervals - is the great need for physical and soul warmth to ensure the child incarnates properly.
So I add these things together and when I hear something like what (List Member X) says about weaning when the child turns her head away from her, I get concerned.( To be honest, I haven't heard that one before.) It seems to me that taking this picture of the baby as a sense organ and needing soul warmth, that extended breastfeeding (ie at least up to around the child's first birthday) makes a lot of sense. And, of course, things like slings, carrying and the family bed all seem to me to be part of this. But.... there's a funny streak amongst many Waldorf early years people which frowns upon all this....
What I have heard is the idea that when the child is able to walk away from his mother, somewhere between 9 and 12 months, that this is a good time to wean. This actually affirms the observations I made when I ran early education and Mom and Toddler classes many years ago. If a baby was weaned somewhere between 10 and 14 months, it was usually no fuss and almost seemed as if the baby didn't notice. It flowed with her increasing independence and moving away from Mama. But if one delayed past that time, one was usually in for the long haul - 2, 3 or 4 years of breastfeeding. This seems to be because of the child's growing awareness of her surroundings - the breast becomes a possession the child does not easily relinquish.
Now - I make no judgments here. I weaned both my sons during this phase with no problems. This was my choice - I did not want to breastfeed any longer and this time seemed to work well for my boys. We co-slept until the eldest was about 7 - the youngest stayed in the bed until he was about 9. This seemed really important for all of us.
Some woman choose to wean earlier, some later. I think that if the woman is clear about her needs and the needs of the child and doesn't get these mixed up, that there is a wide range of "best time" to wean. Many little ones definitely need to go beyond the cut -off I mentioned. No problem.
Back to "what does Steiner think" - or, I should say more properly, what does anthroposophy suggest out of its understanding of the human being - I see 3 years of age as the major change point. Before that? I think only the mother, with her deeply attuned sense of intuition of what each of her different children needs, can say. However, there are pointers which people can miss if they don't know about them - thus I mention this 10 - 14 month phase.