How long a vape pen battery lasts depends on several factors, including the battery's capacity, the type of e-liquid being used, and how often the pen is used. You must recharge a small battery more often than a larger one. The kind of e-liquid used can also affect how long the battery lasts, as some liquids are more taxing on the battery than others. And finally, how often the pen is used will also affect battery life. A pen used frequently will need to be charged more frequently than one that is rarely used.