I can speak a little bit to LED lifespan, from a professional perspective. When an LED, or product with LED’s in it, claims a certain lifespan, even if it’s from a major, up front manufacturer, they’re typically stating the duration after which the lamps were producing either 70% or more commonly 50% of their original output (typically meaning 30% or 50% of the chips are dead).
Heat is a major factor. Run the LEDs at a lower intensity, they produce less heat and last longer. (My neighbour who runs a glassblowing shop has issues with this, unsurprisingly, because of the high ambient temperature)
At work we will often buy higher intensity LEDs and run them at 75% (give or take) of their maximum output, to ensure greater lifespan. (With applications like church lighting, ie high ceilings ensuring higher ambient temperatures, and difficulty in accessing for replacement, we try to overbuild)
I am far from an expert on this. Not to throw him under a bus (of sorts) but if anyone wants to pick my coworker Dann’s brains about this, he’ll probably be at the Ontario meet-up on Saturday. He runs our assembly department, and just enjoys electronics, generally. (Worked at Active Surplus downtown for years)