Here is an excellent article by survivingthesheep.com that shows you how to modify an Eveready 5109SL LED Flashlight with a 150 Ohm resistor to make it last 1000 hours. That’s quite impressive if you ask me, I did this modification myself and it was quite easy.
You simply replace the red wire with a 150 Ohm resistor like in the photo above, it requires a little soldering skill but thats about it. To learn more about the output results using different resistors check out the article below, it goes into more detail.
Read more at… A 1000 HOUR $5 LED FLASHLIGHT