That's weird, because I was just on a planet and stopped in at a "civilized outpost" and after destroying a group of Spacers that was harassing the outpost I returned for my reward and to do some trading. Imagine my surprise when I get to their little store counter and no one is there. And as I turned around to leave (after clearing out the safe) one of the settlers walks by and says "it's a little to early for the store, just come back and someone will be behind the counter later".. so where it may not be a game wide radiant system, it appears that some of the NPCs are on a trimmed down "schedule"...