I promote extended breastfeeding and health. I plan to let my son self wean. Most people drink cows milk their whole life.
Breast milk is far superior to cows milk because it is designed to nourish a human and not a cow. We would have lower health care cost world wide if every woman would allow their child to self wean.
Biologically a growing child needs extra fat in their diet until the age of 8 years old. Breast milk contains fat that is far superior to the type of fat found in common table food. Most children wean from breast milk by age 8 if allowed to wean on their own.