Re: How long to breastfeed?
The answer is that breastmilk never becomes valueless. It always provides nutritional and immunological benefits.
When breastfeeding becomes "not worth doing" is more of a mothering and social issue than a scientific one, and it's very personal. Many moms get tired of nursing, want their bodies back, or feel uncomfortable nursing an older child. Those things often happen long before the baby is really ready to wean him or herself (and yes, babies do self-wean!).
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"