I'm thinking of giving my 5-month-old a bottle of formula at night before he sleeps so he'll sleep longer. Been exclusively breastfeeding all this time. Is there really a benefit to exclusive breastfeeding vs. "mostly" breastfeeding?

It is highly recommended to exclusively breastfeed until your kid is at least 6 months of age as it protects the infant against infectious and chronic illnesses. Exclusive breastfeeding also helps the infant to regulate day and night patterns. Feeding formula in between will disrupt this, thus if you are able to breastfeed for longer, please do! http://www.who.int/nutrition/topics/exclusive_breastfeeding/en/