This slide here shows detailed computation of the battery life that can be achieved using BU33UV7NUX boost DC/DC converter IC. As shown, when the mode pin is low (Fixed PFM mode), battery life of 2.68 years can be achieved and when the mode pin is high (Auto or PWM mode), a battery life of 2.48 years can be achieved. Both of these battery life calculations are based on an output current of 50µA average current during operation. This part can greatly increase the battery life when compared to other similar parts from competitive vendors.