I must be doing something wrong...I've had a horrible time with the two boxes I have. I fill them (I've tried both methods now), and let them sit. They're great for about 3 pulls or so and then burnt plastic taste. Every single one. I've gone through almost 30ml of juice and 8 cartos now trying to get them to work. I'm ready to admit defeat. I don't know what else to try to make them workable.