There is that point, too, where you not have to look up how to formulate something in your new programming language, but can write it just down. Is that not "fluent"?

What do you guys think about learning just one programming language or just one human language? I don't think you can be a real expert in a language, if you just a single one. First, you will not get a good feeling of what the style of your language is, if you just know this one. And second, there is stuff, you can write easy in language A but much harder in language B. There will be a point in mastering language B where you have to be able to write the same stuff, too. But you might never learn that stuff, if you never saw people doing it in language A. (pg's argument for stronger languages vs. weaker languages is some kind of subset of my second argument)