So I haven't been to too many milongas, but one thing I learned recently was that you stay with the same partner for a whole set of music. You don't change partners after each song. Let me know if you disagree, and also what else might be helpful to know in terms of etiquette. One partner told me this when I stopped. Then I said, well let's go back out, and she said that would be strange, because you only stop if you just can't dance anymore. I didn't completely get it, but maybe I have a lot to learn.