I like a lot of detail in my settings, so "three and out" is about completely opposite of what I want in a setting. I don't necessarily need a constant stream of new mechanics, but I'm always thirsty for new places PCs can visit, new characters they can interact with, and new events that can have an impact on them. Luckily my setting of choice these days has a huge wiki devoted to it, so I'm seldom if ever short of material.