Okay here is a question....for the DSE901 they say to charge the original batteries 8-12 hours. My question is this. I will be using the passthrough while at home for the most part. If I have batteries fully charged, how long do they stay like that? If they are fully charged and I don't use them that day and just have them sitting around and use them the next day when I go out, will that be okay? What about when they say they last 4 hours does that mean 4 hours of vaping or withing 4 hours they are dead no matter what you do?