CPF member NewBie did an extensive set of tests looking at how to reproduce the Roar of the Pelican incident. This thread is a must read for all who use multi cell CR123 lights.
This ended up being a collaborative effort and some important lessons were learned.
Use quality cells in multi cell lights. (Since this happened BatteryStation has changed suppliers of CR123 cells and now is offering high quality US made cells.)
When the light goes out, shut it off.
If the light gets hot in your hand, shut it down and let it cool off, if possible.
Check the condition of your cells. If you notice some loss of charge due to passivation during storage, those cells are not suitable for high drain use.
Suitable testers are the ZTS and checking the voltage under some sort of load.
There is a whole lot of other information in this thread, so my short list is far from being exhaustive.