Have you compared sessions where you're principally, say, reading books with a bookreader app vs. Web browsing, or using other apps?
My experience on the BOOX, an E-ink device, is that web browsing (Einkbro) consumes battery at ~10x the hourly rate that reading books (Neoreader) does. How much of that is active display, and how much is other CPU usage, I don't know.
My experience on the reMarkable 2 is that leaving it "off", showing the screen it displays when it detects that you haven't done anything for a while, will drain the battery in a matter of days, whereas leaving it "off", showing the screen it displays when you manually navigate into the shutdown menu and tell it to turn off, drains the battery in a matter of months.
I assume that none of the difference is in active display; the display is static in either case.
The Remarkable2 is an E-Ink device. I'd asked mattkevan as they are using a transflective LCD-based "E-Paper" device.
The technologies have a similar appearance, but utilise different technologies (electrophoretic vs. liquid crystal). Principle differences are the responsiveness of the display (LCD is far faster) and power consumption (LCD draws constant power, the display clears when voltage potential is removed, electrophoretic displays persist indefinitely when power is off).
As I'd noted in the comment you're replying to, I've used an E-Ink device for years, and am familiar with its power consumption characteristics.
Have you compared sessions where you're principally, say, reading books with a bookreader app vs. Web browsing, or using other apps?
My experience on the BOOX, an E-ink device, is that web browsing (Einkbro) consumes battery at ~10x the hourly rate that reading books (Neoreader) does. How much of that is active display, and how much is other CPU usage, I don't know.