As silly as it sounds, it's a good idea to save some of your depleted eCigarette butts. What I am talking about are the nicotine cartridges that you would normally throw away. It's very easy to overlook reordering the nicotine disposable cartridges and suddenly discover you don't have enough cartridges to last until a fresh shipment can be delivered to you. This could lead to disaster. If you run out of nicotine cartridges and don't have any other source of nicotine, you might just be tempted to buy a pack of tobacco cigarettes. This is a something you absolutely don't want to happen.
When you have pretty much used up a cartridge and you are just getting a little bit of vapor and hardly any nicotine when you take a puff. Put both of the soft rubber end caps back on that cartridge. Stash the cartridge away in a secure place and accumulate several cartridges this way.
What you will discover is that after sitting for a few weeks with the rubber end caps in place, the disposable cartridge will 'come back to life' you will be able to get anywhere from 2 to 6 good hits from each stored cartridge. Sure, it's a pain in the rear to have to change cartridges after only a few puffs. But it is far better than falling off the wagon and lighting up a tobacco cigarette.