My baby was 6mths and now is 11mths.
I feel that it depends from baby to baby to sleep through the night. Average is probably 6 mths. My baby slept through at 3 mths. Usually if baby had enough to eat in the day, they would tend to sleep through the night. My baby was also on a routine and I just slowly dropped feeds that was how hubby and I "trained" him.
My another friend's baby slept through at 10mths and another at 1 year.