Had a quick foray into night MTB riding but I found that it wasn't for me. Up for sale is the light I bought for said riding. I think it was only sold at Performance Bike, I bought it in January of this year...the battery has been charged to full power twice and the LEDs have been "on" for a grand total of approximately 3 hours. Lots of life in both the battery and the light.
Asking $125 OBO shipped, includes light, battery and wall charger. Here is a link to the unit and a pic.