Do lithuims just go out without warning?
I have the mc 3b combat light, got it for christmas, I knew it only had 1 hour full power with the batteries, after that it lowered in intensity as expected, even so, down some from 125 lumes it was still a heck of a strong light.
After maybe 20 minutes of lowered light,  I was using it and turned it off, about 10 minutes later turned it on again but it wouldn't work, I finally changed the batteries and it worked.
Do lithiums go out that quickly?  Most lights get dimmer and dimmer and dimmer.
This was a night day difference from works to out. Is that common?

I'm not sure if this is true in the model you have but some Surefire's control the output specifically to drop to a low but useable light, giving the user notice and time to replace the batteries, then go out IIRC.

Do lithiums go out that quickly?

Sounds normal.  When they start to go dim, its quickly time to change them.

Quoted: Do lithiums go out that quickly? Sounds normal.  When they start to go dim, its quickly time to change them.

+1

SureFire digital lights will dim and still run for awhile, the others pretty much go straight out.

appreciate the info, valuable to know so I can have batteries around.

I guess I should have mentioned, it is a characteristic of lithium batteries themselves to have a long power output that does not go down very much in voltage, then to sharply drop off at the end.  It can make remaining power capacity difficult to determine.  Some devices I have must be told that lithiums are being used so the power remaining meter is accurate.

While it sucks they drop off at the end of their life leaving you with little to go on while swapping batteries, it's good because the device remains at near full power until close to the end rather than have dimishished capacity for much of it's battery life, or insufficient power far before the battery is fully depleted.

Get some spare lithium batteries and keep them handy for when you need to switch.  Lithiums have about a 10 year shelf life so no worries about storing them for years, they will still be good and retain most of their charge unlike alkalines and carbon zinc.