I am breastfeeding five to six times a day and she has normal output. She regularly sleeps through the night, from about 10pm to 7am. Though her doctor says it is okay to let her sleep through, I have heard that babies need their nighttime feeds. She is a Board Certified Lactation Consultant, as well as a retired La Leche League Leader.
Many babies do get a good portion of their nutrition from nighttime feeds.
It sounds like your baby is thriving and sleeping through the night. Most babies this age are nursing at least eight times during a 24-hour period. Frequent nursing provides your breasts with the stimulation they need to maintain a good milk supply. I would recommend increasing daytime nursing sessions. Try feeding your baby on cue.