It's not as interesting as I make it seem. At the end of the day, it's just a flat multiplier. It'll take a few weeks or even months of somewhat involved play before you start reaching the point that the completion tokens start noticeably changing the game's pacing. The game itself is not that much fun to play without this system.
I like it for the reason that the dev didn't seem to have accounted for people grinding that bonus after completing all released content - but I'd expect that most people would not feel the same way.