Good points, James. It's important to identify the most extreme situation you will reasonably face, and match your light to it.

Fenix lights are "dunk proof" and that's about it. I wash them in the sink, but wouldn't rely on one for life raft use.

I also think that, in a critical situation, a backup light is always a good idea.

BTW: In my experience, AA lights that use LEDs are surprisingly useful, even in very cold temperatures. The output drops, of course; but snow is very reflective, and even a low-output LED does a remarkable job. It helps to keep the light in a protected inner pocket when not in use. (It's also quite a shock when you return it to that pocket after a stint in the cold -- yikes.)