Mine are 3 years 2 days apart, and I like that spacing. Close enough that they'll still play together some, but far enough that the oldest was quite independent by the time the baby came (out of diapers, able to speak and care a bit for herself).
I do think it depends on the children and on the mom and no single answer will be right for every family.
For me, I definitely want to nurse a minimum of 2 years, and it has to feel right in my heart and for my body. For my parenting style and my body, 3 years is my minimum, and when we have #3 it will probably be a bigger then 3 year gap (or at least that's what I think at this point

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