The brightness of a device can have an impact on its battery life. The longer the battery life, the brighter the screen, as your device consumes more power with a brighter display. It is advised that the screen brightness be reduced to maximize battery life. As a result, on your iPhone 8 Plus, alter your display settings and reduce screen brightness. Here's how it works:

1. To access the Control Center, swipe up from the bottom edge of your screen.
2. Drag the brightness bar down to increase or decrease the screen's brightness level.
3. You can also go to Settings-> General-> Accessibility-> Display Accommodations and drag the slider to the left to reduce the screen brightness.