I will not notice the effects of graduation only in a graduated way. I lose half of my friends this year, but I don't leave until next. I guess the experience will not be quite as jarring that way.
Anyway, I think it a crime if we all didn't keep up in some meaningful way. I don't want Christendom to be some cruel twist of fate which puts us all together, as us form attachments, and then violently separates us all. Granted, we need to find a new basis for continued friendship since we no longer have Christendom has an everyday common experience. It will now be only a common memory. However, a new basis can be found, and I think that it would need to be based on the high standards of intellectual goals we all pursued in common for so long.
If we limit ourselves to fluff talk, we will not keep up in a substantial way, but if we constantly discuss issues, we just might.