In my experience, a Kindle connected to wifi burns through battery like there's no tomorrow. Like a percentage point every half hour. I absolutely keep it on airplane mode to preserve charge.
It really speaks to the longevity of the Kindle that 50 hours of battery life ("a percentage point per half hour") counts as "[burning] through the battery like there's no tomorrow."
Or maybe it speaks to how little time most devices last, I can't tell.
(To be clear, your expectations are reasonable, as battery is a key selling point of e-ink Kindles.)
I remember when I migrated from a flip phone to a smartphone a few years ago. I have been frustrated for as many years. One day I realized I could just buy a charger for every location I might stop for a while. Now I am not frustrated at battery life. I am frustrated with the solution.
It is not unlikely that this will be my next phone: https://www.thelightphone.com/
I love the idea of an e-ink phone.
> The battery life of the Light Phone II is approximately 1-3 days of 'light' regular usage.
That's roughly equivalent to my iphone. I love the idea of an e-ink display, but it's not clear to me that this saved enough, on its own. Maybe the lack of entertainment/social/goof-off apps will reduce your use so much that you frequently hit maximum theoretical battery life? Is that the justification?