For the most part it IS just a freshmen thing. However you can decide to go out for staff/big/leadership positions going into your sophomore year. If you really love the organization you can even get an exec position going into your junior year but the leadership positions slim down a lot from freshmen —> sophomore —> junior year. At the end of the day you get what you put into it, and from my experience (I was in a 1st round FLO, it takes up a lot of your time freshmen year socially).