Does the screen brightness decrease the overall life?

Would like to point out that white LEDs, as are commonly used in LCD backlights, are phosphor-based devices, e.g. there is a "white" phosphor that is excited into illumination by some other wavelength of light. Perhaps the LED semiconductor itself emitting the primary (and unseen) wavelength is not aging much, but the white phosphor overcoat most definitely is aging and will dim with time.

Yes, the life span of any light source, including LEDs, will be increased by running them at reduced output. Furthermore, they degrade with time, so even though the setting will be at maximum throughout the life span, the brightness will be subtly yet continuously decreasing.

But the life rating on backlight LEDs is long. How much life span were you looking for? Will the displays be running 24 hours a day, 7 days a week?

If you do a Google search on LED Display technology, you'll find that the advantage over a standard lighted LCD displays is that light output DOES NOT degrade over time. Meaning running your display at FULL brightness will not shorten it's life or make the display 'dim' over time. Having an LED display ON, regardless of brightness will shorten it's life, but LEDs last 5 to 10x longer than the standard CF lights normally used.

Unless you plan on having it on 24x7 ALL the time, an LED backlight will outlast the useful life of the display you're using. Set it to automatically go to sleep when you're not using it and don't worry about about how high the brightness is. It will be just as bright 5 years from now as the day you bought it.

All true, but the effect of having the display at FULL brightness as opposed to 75% brightness is negligible. It's also not going to age anywhere near as fast as the CF lights in standard monitors. You'd have to have the display on 24/7 for years before you noticed any decrease in light output. As I stated, the backlights will far outlast the useful life of the monitor, except maybe the one in a million person that might want to buy one and use it for 10 years.

Yes, I agree with you completely. I was just trying to answer the OP's question of does the screen brightness decrease the overall life of a display? Simple answer: yes. But I agree that the life should far surpass most people's needs.