When this happens, it becomes a daily thing. For the most part, I just want to make sure that the seller has not forgotten about me. I know that this can be a little annoying, but it's odd for such a long period to go by between milestones, except for confirming a personal check. Still, it's good to keep in touch, even minimally. I'll just say that if you feel that the deal was bad, and that such action is fully warranted, and if you have given the seller every chance to make good, then go ahead and do it, but make really sure.
Some sellers leave feedback as soon as payment is received.
Other wait for you to leave it first. I don't mind this, and as a buyer, I leave feedback as soon as I get the item. Once that happens, I inform the seller that I have done so and very nicely ask for positive feedback of my own. As of this writing, about 8 sellers are on my no-list. I know that feedback is voluntary and all that, but it's important to me.