The Princeton Tec EOS is, IMHO, a great caving backup light. Or even primary light depending on your needs and preferences. It has a broad flood with a bright central spot. Battery life is great and weight is minimal.
But MINES!!???!! I've been in lots of caves, but mines scare me - they are notoriously prone to collapses and floods, etc. even when freshly maintained by experts. Caves are much older and, IMHO, more stable. Your mileage may vary, though, as caves are certainly dangerous enough.
General note: Caving can be dangerous. Caving without three (preferably more) RELIABLE, ADEQUATE (to get yourself safely out of the cave, with more than plenty of margin)sources of light is suicidal.
If you are involved in any caving "work" (such as mapping, rescue, cleanup, etc.) the rule for "adequate" is tougher - adequate to complete the mission at hand, without any inconvenience to fellow participants. You can't do real cave work with a
MiniM@g held in your teeth.
I am aware that in some countries it is common for each participant to carry just one light, with a communal spare carried by a designated person. This is extremely unwise. I see no justification whatsoever for this dangerous practice which, as a provincial American, I attribute to European Socialist leanings. /ubbthreads/images/graemlins/smile.gif
I often read here and elsewhere on the internet about people that cave using only flashlights. A flashlight is a handy thing to have in a cave, but a headlight is a must. Of course, a flashlight can be mounted to the side of your helmet. If you're actually going to cave WITHOUT a helmet, you might as well go ahead and bash your head against the nearest brick wall now - it will save the EMT's/coroner the trouble of getting all muddy.