Whoa, take it easy over there! Quite frankly, you can do whatever you like, but we wouldn't recommend over-shaking. Actually, don't shake it at all. In general, the "Rumbling" step (i.e. agitation) is just intended to soak all the grounds in water. Over-agitating definitely won't make better coffee, but it definitely will make more silt/sediment! If you're brewing with the barista-recommended coarse grounds, just rotating the jar 90 degrees until it's horizontal a couple times should be plenty. To watch proper rumbling in action, have a look at "Step 2: Get your rumble on" in our Brewing Instructions pageAnd if you're using fine grounds, don't worry...we won't rat you out to a barista. But you may want to add a couple more rumbles if you're noticing the dry grounds issue (see related FAQ).