Well for the unlucky players such as myself, you will get a key in approx every 50-100 nm nanos you obtain. If you're one of the lucky players, then it'll be more often than that.
Another way to put it is, play 5 nm tix a day, (winning as many as possible), and you'll likely get 1 core a month, and a key every 1-2 weeks. That's pretty much it.