To me it's a limited-challenge game. I don't really roleplay -- if I wanted to tell stories with a blank sheet of paper, I'd write. And I'm not super interested in map-painting. So usually I pick an achievement or two that go together, or some silly combo of things, do that, and stop playing for a while. The last game I did was finishing the Persian intermezzo with the pro-Caliphate ending as an unlanded character, a thing which broke my save completely.