Is the key for battery lifespan.

And there is a bit more to research in this field. For example if the VCC consumption of this Eink is below 12 mA why don’t to power it with a gpio of our Espressif board? 

That will keep it from draining unnecessary energy when we are in deepsleep. Doing that simple improvement and taking control of the VCC took the deepsleep consumption from 1.3 mA to 0.84 mA

Here is the proof of concept update: https://github.com/martinberlin/eink-calendar/commit/978d062e7fcd446acce91535a6a3a0db4df43762

Needless to say, but check what is the max consumption that is allowed in your microchip specs, going over it may damage your board!