Das Ronin, this is actually a back-up lamp in case I can't get to the main one, or, as you note, if the primary one fails. I'm also going to have 1 or 2 others, as further back-ups. I used to be really into training and preparations but kind of fell out of that just due to other responsibilities and hobbies. Now, I'd like to get back in, but in moderation. I understand there is more involved than just flashing a light in someone's face, and that the most important "tool" is the brain, and by extension, past knowledge and training. I just want to optimize my illumination tool. I have no doubt that the C3 is probably one of the best lights for this task, but if the M4 is better, even slightly, than I'm going for that. At this point, I haven't even received the C3 so I could easily sell it (when I get it) and be half way to the M4. In regards to the 20 minutes of run-time, that should be enough for my needs but if given a choice, of course I'll take 60 minutes over 20.