Honestly, I'm just using regular carts and I cut the filler in about half to make a plug. I can get around 15-18 drops in it and vape it for about an hour or so before it's dry. That's right. I said dry. When the only juice that's left is what's in the filler, it just stops making as much vapor and I know it's time to refill. I've only had one leak, and that was my mistake for not making sure the plug was in there right.