[tanzam75]

No. In fact, the LED lifetime stated on the packaging is actually the time it takes to decrease in brightness to a specified reference level -- usually 70% of initial brightness.

Since it is solid-state, though, the LED is expected to continue operating long after it reaches 70% brightness. 70% is simply the assumed reference point at which the consumer becomes annoyed and decides to replace the LED.

Source: Department of Energy, "Lifetime of White LEDs", http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl...

> the Alliance for Solid State Illumination Systems and Technologies (ASSIST), a group led by the Lighting Research Center (LRC), recommends defining useful life as the point at which light output has declined to 70% of initial lumens (abbreviated as L70) for general lighting and 50% (L50) for LEDs used for decorative purposes.

[hcarvalhoalves]

Even the new generation LED lamps are like that (Cree X and such)? I read something the other day that suggested these LEDs were immune to losing efficiency over time (the efficiency would be dictated only by heat).

[tanzam75]

Yes, LEDs will last longer without heat issues. But unless you're running the LED in a refrigerator, that's not a particularly informative statement.

As stated in the DOE that I linked to: "The primary cause of LED lumen depreciation is heat generated at the LED junction." Because it's the primary cause, you can't just ignore it and say that LEDs barely degrade in the absence of heat. You have to consider the heat when calculating LED lifetime.

The stated lifetime on the LED packaging makes a number of assumptions, one of which is that the LED is run at room temperature.