I know nothing about trail/MUP riding since there is no such thing where I live. As for riding on the road, I'll stop turning my lights up to maximum when I am confident that I can do so and not have the car with my name on it "not see me"
With my current lighting setup, an original MagicShine (450 lumens, no cutoff) on full brightness, I have had cars with clear lines of visibility for 1/2 mile, no distractions at all and me wearing neon green reflective wear "not see me" and pull out and hit me. Clearly I need even more light.
If I were riding on an MUP I imagine that I'd turn my lights down considerably. I already do if I'm out on lonely stretches where I can ride for 20 minutes and not see anyone else.
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Work: the 8 hours that separates bike rides.