Theoretically, gunking occurs in the chamber and are enclosed, juices slip into the juices channel to wick the cotton, by right you can redraw the juices and transfer it back to the juice bottle. But most will not reuse after vaping leftovers, each time the juice is expose to air and moisture and sunlight, you loose the level of nic and those high VG will also be more diluted
Most tanks are around 4ml more or less, so it would be better to vape till the juice are gone in the tank
Unless you don't have extra tank, transfer back to the bottle and use the same bottle again
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