Stability studies of nanosecond light sources based on blue ultra bright   LEDs
  We present the results of stability studies of nanosecond light sources based on single quantum well (SQW) InGaN/GaN ultra bright blue LEDs. It is shown that the light yield of such light sources and their timing characteristics don't deteriorate even after 10^10 total pulses. The longterm stability of the sources light yield is better than 1%. 
B.K. Lubsandorzhiev, Y.E. Vyatchin