All I can say about our experience is that we're at 15 months of breastfeeding, with never a drop of formula, and never will. She's in the 97th percentile weight, 75th height, and has never been sick, save for one two day cold and two bouts of carsickness.
This is what the WHO recommends:
The World Health Organization recommends that infants should be exclusively breastfed for the first 6 months of life. Breastfeeding should continue for at least 2 years with weaning foods added at 6 months of age. A weaning diet should consist of:
a staple (a complex carbohydrate) such as cereals, roots, or tubers,
an energy rich supplement (fats, oils and sugars),
protein rich supplements (legumes, animal products, meat, eggs), and
vitamin and mineral rich foods (fruits and vegetables) ( WHO, 2001 ).
these complementary foods should be low cost and prepared locally ) WHO, 2003-3 ).
The American Academy of Pediatrics recommends breastfeeding for at least 12 months and as long thereafter as mutually desired. Supplemental foods should be added at 6 months of age ( AAP Breastfeeding, 2005 ).
In 1989, The World Health Organization (WHO) developed the Ten Steps to Successful Breastfeeding. Every facility providing maternity services and care for newborn infants should:
Have a written breastfeeding policy that is routinely communicated to all health care staff.
Train all health care staff in skills necessary to implement this policy.
Inform all pregnant women about the benefits and management of breastfeeding.
Help mothers initiate breastfeeding within a half-hour of birth.
Show mothers how to breastfeed and how to maintain lactation even if they should be separated from their infants.
Give newborn infants no food or drink other than breast milk unless medically indicated.
Practice rooming in: Allow mothers and infants to remain together 24 hours a day.
Encourage breastfeeding on demand.
Give no artificial teats or pacifiers, also called dummies or soothers to breastfeeding infants.
Foster the establishment of breastfeeding support groups and refer mothers to them on discharge from the hospital or clinic.