I am thinking about buying a Marc Jacobs quilted stam. In some pictures I've seen on eBay, I notice the bag seems to sag when it's not being held up. I had an LV Speedy that would sag easily, and I hated that. Ended up selling it on eBay because I couldn't deal with the sagging. Is the Stam this way too? Or does it stay "up" when you put it down on a hard surface?