LO has been sleeping through the night since about 2.5 months (yes, we know, we have a jackpot baby). On the rare occasions she wakes up in the middle of the night and doesn't go immediately back to sleep, maybe once every 3-4 weeks, we give her a small (2 or 4 oz) bottle.
We figure what happens is that once she wakes up, she realizes she is hungry and won't go to sleep until she is not hungry. But she's not hungry enough at that time of night usually to wake her up.
The first couple of times we did it out of desperation, frantic that this would mean she'd go back to wake up for middle of the night feedings, but this has not been the case.