600 minutes = 10 hours, which is actually only so-so given the output level. This is because the LM31 uses a resistor to drop down to the low level which is VERY inefficient.
The Jetbeam C-LE V2.0 'clicky' version has 5 modes (with memory so it is as simple to use as a 1 mode) and the low mode is brighter, and runs more than TWICE as long.
Both lights would do the job, though if you like simple clicky operation, you should note that with the LM31, you have to cycle through HIGH every time you want to turn the light off (which is quite distracting in a bedside light).
It is true that with the LM31 there is a trick involving turning the front bezel as a 'twisty' switch so you can turn the light off without cycling through the high mode, but with the C-LE the memory lets you just turn the light on and off in low mode once it has be set, just like a single mode clicky light.
I like the C-LE, it also has a nice medium mode for when you need it, has better output and runtimes, and cost a few bucks less.
Also I worry a little about the complicated 2 stage clicky switch of the LM31, even big name companies like Surefire and Fenix have been burned with clicky switch problems, so making this switch more complicated than necessary does not give me a warm fuzzy feeling (though, so far at least, their have been no reports of problems of the tail switchs of either the C-LE or LM31).