You can see more about how the lamps were originally tested here:
The DOE, however, didn't stop testing the light bulb in 2011. 4 years later in August 2015, the Philips L Prize bulbs are still running strong. In fact, with 31 lamps tested, not one has failed! Even more impressive, they've retained an average of 95.6% lumen maintenance. All bulbs lose brightness over time from different factors, but these bulbs have lost very little.
In terms of lumen maintenance, failure in an LED bulb has been defined as the bulb dropping to 70% lumen maintenance. (That means it has lost 30% of its original brightness.) Based on the tests of these bulbs so far, it's estimated that the average bulb (barring other failures) would last nearly 200,000 hours before reaching failure lumen levels.
Finally, the bulbs also retained their color quality almost perfectly.
For more details, please visit LEDs Magazine. Or visit us online to see the latest in A19 LED technology.