One guy went out every day for the first semester. This isn't the norm though. For the rest, I'd say about 5-6 extra times until about the middle of November, before it stopped. Then for special occasions, such as Christmas, but I can't think of any other time.
Im assuming you mean going out to a club or bar. It entirely depends upon the person/people. I know some groups of people that went out once or twice a week, others 3 to 4 times a week (even after freshers - some for most of the year) and some people who stopped going out at all after freshers.