You will know it is time to replace your Elf Bar with a new one when the flavour starts to deteriorate and less and less vapour is being produced with each inhale.
The Elf Bar features a LED light that will flash to alert the user that the device has run out of e-liquid and it is time to replace it with a new unit.
As with all vape products, there is no hard and fast rule as to how long something will last you. Whilst they do say 600 puffs capacity each user's puff will be different from another user.