When the flavour of your Elf Bar begins to decay and less and less vapour is created with each inhale, it is time to replace it. The Elf Bar contains an LED light that flashes to notify the user that the device has run out of e-liquid and needs to be replaced. There is no hard and fast rule for how long something will last you, as there is with all disposable vape products. While the manufacturer claims 5000 puffs, each user's puff count will be unique.