I tend to agree with quimby. I'm a bit sceptical about sales because in the past I've sometimes bought some "this is quite okay"-pieces because they were a bargain. I prefer buying the stunning piece that I truly love for the real price than several just-okay pieces.
I still buy on sales. But I try to be very focused and keep to my lists, especially on sales. If a wardrobe staple like a striped tee or a well cut black top is on sale, why not. Or a piece I've adored all season but couldn't afford it. But I buy full price, too. On the online shopping pages you can observe that very often the best pieces sell out within few days, so you'd rather be quick than wait for the sales.
So, after all, "bargain" is not the main criteria for me. "Love" is