It all depends on your area. 80-90% means nothing to me if they can't cover them all or if the queen hasn't laid up all the area she can. If you want frames drawn out quickly, you let them get a little crowded even, then you can add a box, checkerboard them and they'll have them all drawn out and laid up in 3 weeks and ready for a third box. Of course this all depends if there's a flow or not, if you're in a heavy flow it's good to stay a little or even a lot ahead of them but moderate to slow flows it's best to wait til they actually really need the space before giving them any.