Black and white Kindles aren't just easier on the eyes—they're champions on battery life. The core reason is that e-ink displays only use power when the screen actually changes, like turning a page. A color screen, even an e-ink one like on some newer models, has to refresh tiny color filters constantly, which drains the battery much faster. So, if you're the type who reads for hours on a single charge during a flight or a weekend camping trip, that monochrome display is a silent workhorse.
I've had my Paperwhite for years, and the battery anxiety is virtually non-existent. I charge it maybe once a month with daily use, and that's with the front light on at a low setting. It's one less thing to worry about, which is honestly half the appeal of a dedicated e-reader versus using a tablet. You're not fighting against notifications and background apps sucking juice; it's a device that exists purely to hold your place in a story without interrupting you for a power cord.
Some people might find the lack of color a dealbreaker for graphic novels or cookbooks, and that's fair. But for prose-heavy fiction and nonfiction, the trade-off is overwhelmingly in favor of the black and white models. The longevity becomes a feature you stop noticing because it's just always there, ready to go, which is the best kind of feature.