We all know that LED brightness decreases with age. An exit sign in Vassar’s Skinner Hall shows what that looks like in real life:
The LEDs on the other side of the sign look about the same: a few very bright spots, a few very dim ones, and a whole bunch in the middle.
It’s hard to judge by eye, but the brightest LEDs look much more than a factor of two brighter than the dimmest ones.
An LED with a 50,000 hour lifetime will have 50% of its initial brightness at EOL and a year has 8,766 hours, so the LEDs will reach half-brightness in a bit under six years. I think discrete LEDs went out of style around the turn of the millennium, so it’s three half-lives old: the dimmer LEDs must be around 1/8 brightness.
In case of an actual emergency, just follow me out the door, OK?
The Smell of Molten Projects in the Morning 