My device is now running for about 6 days with one battery charge. But I'm using deep sleep mode now. If I use disableEPDPower() before getting into light sleep mode, I need to re-init the display after wake up. So the advantage of light sleep is lost and display need to be fully updated. I choose this device with e-paper display to build a low power application, but at the end it was not the best decision to use M5paper.