I have the same problem, and it exists on your demo as well. There are actually a couple of problems. When you make a discount and it is a dollar amount no discount is applied. If it is a percentage it is applied, but if you want the discount only to apply until a certain day, the discount disappears. Something needs to be redone in the code. Also, I am not sure why there is not a sale price area, meaning for a limited time the price is $100 on sale from $120 and the $120 has a strike through it. Even if it is factored into your discount right now, a lot of shop pages will show the first price striked through, then the discounted price. My client right now is asking for this, but I have to build a work around.