Am I going to run out of articles to translate after a while? I don't know if there are only a limited number of them available. If I have nothing left to translate, I will lose my place in the leader board :)
I think the idea of duolingo is to translate the entire web through your practice. So theoretically, you should never run out of things to translate, because the web is pretty huge, even en español.
I'm not sure if they have made the whole Spanish web available for translating yet though. I'm sure they will have more than enough ready to translate soon if they don't already though.