You will realise that the time has come to replace your Bloody Mary disposable in one of two ways. Ideally you will notice a flashing led battery light and loss of vapour which means that the pre-charged battery is now empty. Or, if the e liquid tank is empty but battery power remains, you may experience a 'dry-hit' which is a fairly unpleasant taste from the heating coil element. Bloody Mary try to avoid this second scenario in the manufacturing process.