Hi. I have an e mini ciggie which I've been using for one week. I have two batteries which I charge alternately. I have just changed the battery to a fully charged one, as the other was flashing to indicate the battery was flat, and the charged up battery which I screwed in isn't working. I plugged it back into the charger, just to double check and the light is green. I took it out and tried again, but the end of the ciggie is still flashing. Are the batteries only supposed to last for one week before they pack up? Thanks.