Running LEDs on low voltage for long time
They will probably last longer because they are drawing less current and should run cooler.  

Understanding the Cause of Fading in High-Brightness LEDs


  The most important factor under the control of the design engineer
  that does influence longevity is junction temperature. Operating the
  LED according to the manufacturer’s thermal guidelines will reduce the
  rate of crystal degradation and ensure a long and bright operating
  life.