I work one job at night in a place that has way too many elecrical problems

The lights have gone out more than once while I've been there and luckily I have 2 below-par lights and a headlamp. But I am looking for something to really get the job done. My spec needs are-
- 250+ lumens
- A low mode with looooong runtime
- Not toooo heavy as i might take it camping/hiking
- I don't really mind what cell it is, and body style doesn't really matter.
- water"proof" is good, but not a deal breaker
Right now I have my sights on an Olight m20s-
http://www.olightworld.com/product_show.asp?id=175But that 600 hour low mode sounds too good to be true