How does one assess their back-up light needs so they know exactly what kind of back-up light will work for the kind of diving they plan on?3 hours might be a bit short for my needs as a backup. Not bad for an emergency light though.
For example, I don't know of a time when I will be on a single dive for longer than 3 hours (including looking at "technical" dives where the worst case scenario has me doing deco on back-gases for the maximum amount of worst case dive time). But for others, a 3 hr burn time is not enough.
I am curious how each of you assess your back-up light needs and perhaps what kinds of back-up lights you use. Currently and previously I have owned the following:
Current
OMS Vega - 3W LED, burn time 3 hrs, 4.26" long and 1.5" in diameter, 330" depth rating!
Previous
DiveRite - 7 LED, burn time 30 hrs, 6" long and 1.75" in diameter (couldn't handle pressure 150'+ although it has a 180' depth rating. It flooded on me in NC at 120'. I sent it back to DiveRite to replace.) Dive Rite and OMS had prevously sold this light, but they no longer do. I think I know why...
Dive Rite - 1W LED, burn time 8 hrs, 3 different brightness levels, on/off switch,
UK SL4 - 5.5W, burn time 4-5 hrs, 6.2" long. I really like the on/off switch which make me a whole lot more comfortable that screwing a light head on and off! It's a little bulky as the body holds 4 c-cell batteries and it can be a little interesting loading the darn thing!
PC Light - 6" long. Lend it as back-ups for my night diver student. Nothing terribly amazing about this light, but it is inexpensive to have in my back-up student accessible tub-o-lights.
PC Light - 5" long. I found it on a lake clean up dive!! Left the batteries it had in it for months and it always turned on when I needed it. I later flooded it because I was stupid and didn't understand how to properly care for o-rings! I miss that silly little pink with a bottom of the lake story...