Well, I can tell you this much; I graduated in 2009. I graduated with a huge friend pool of 24 people, with 6 more graduating the year before us so really it was 30 of us altogether. We were all part of a videogame/anime club in highschool. We hung out there and at the library down the street from the school. But now 7 years later I rarely talk to any of them except for my 3 best friends. Its hard to believe that out of 30 good friends that I got to know going all the way back to 6th grade I only kept in contact with 3 of them. Oh I see em on Facebook and Online via game consoles (Xbox & PS4) or even at anime conventions, but we dont all talk like we used to. And Im okay with that.
Its just feels weird sometimes how you meet and know people all your life i school and then after school ends it feels like the first day of elementary school all over again lol. But trust me if you can keep in contact with just a couple very close friends like I do, and they do the same it wont be so bad.