I have an LED light specially designed for a long run time. It's the Tritiled from Ted Yapo. It runs on a button cell with a microprocessor that turns the light on and off so fast, the human eye cannot detect the flashing. It's been running on my table since July 2016. It uses a special cyan LED because the human eye can see cyan better, which means the LED can use less power but the light can still be visible to the human eye.
This device could have usefulness in marking trails at night, or marking other things in dark places.
This device could have usefulness in marking trails at night, or marking other things in dark places.