do people in greek life still talk after graduation?

It does help with networking in terms of jobs. With my own experience I have seen alumni from my sorority come back and socialize with us but I can’t speak for what may come after. You’ll probably have to devote yourself fully to the philosophy if you want to continue networking with people within the Greek life. People do tend to move on once they graduate.

depends what organization you join, if the brotherhood is tight and matters to them its most likely that you will have these people as friends for life.