I myself even with night adjusted eyes need at least 3-5 lumens, the brightness of the piggy light from dx is great, just wakes up other people. And by moonlight modes, I’m sublumen levels! * How many times a month do you guys really sublumen modes? And on what type of lights (reflectorless, deep reflector, shallow reflector)?* Because I’ve seen a discussion about this over at CPF, but they didn’t say what kind of lights they use the moonlight modes on. Also, if you could say what type of area you live in too: boondocks or the suburbs/city.
The sub lumen moonlight mode I use every night to get to the bathroom without waking my girl up. I like a more floody beam for this an XML with a shallow OP reflector. I use a higher 3-5 lumen for walking around outside in the dark if I know there is no wildlife around again more flood is better otherwise I end up scanning back and forth.
Most of the time at night I’m getting up from a monitor and <1 lumen isn’t enough if I’m just doing a quick errand and that’s important since we have steps down and up going each direction across the house.
But it does work fine if I’ve been in the dark for a few minutes and am just doing simple stuff. Even is rooms with enough general light, it is enough light to do simple things in darker areas, so I’ll use it to plug in cables for headphones, USB cables, etc. I haven’t used it for a night light, but I could if we didn’t already have plenty of light from equipment leds.
In a theater we use it to avoid tripping/stepping on people and to see steps if the theater lights aren’t good. It’s safer and much less annoying than using the cell.
When monitoring activity outside it is handy for navigating inside the darkened house or outside to preserve my night vision.
I also used it during late night drives (did about 4,000 miles this last week) inside the car to look in bags, plug in chargers, etc. without waking our 3rd driver.
Edit: 2100 XML and T10 XPG are used for firefly modes, these are my EDC lights so they are always handy. The XPG is better for walking inside and the XML is better for weak room light (T10 is brighter of the two). Outside both are good because they don’t draw a lot of flying insects like a bright light will do. We have no outside lights front or back of the house except moonlight - a little light does a lot.
I use moonlight every single day, especially when I'm working on something small, like a flashlight and I don't want some uber bright reflection in my eyes.
Foy
I use my dim red-orange Arc AAA when I really want minimal wake-others light. Wish it were a flood instead of a spot beam, or that I could find a newer light in the same range.
I use very low level light quite often. Nowhere as low as I could’ve used 40 years ago when my eyes were younger and my pupils got much wider open in the dark, though. Back then I could see my way in the woods on a moonless night by starlight without falling into the river. Now, the same scene would be just about complete black but for the flashes and sparkles from the aged retina.
I like tailstanding lights and anything less than 5 lumens doesn't suply enough reflective ceiling bounce. I just got my first low E1320 light and love the low mode, use it every day ! I need to get a .002 lamp to try ....... :)
I use whatever is nearby but whether it’s 1-2 lumen or .2 lumen either will work for walking around the house late at night.
If I’m camping .2 is better in the middle of the night in the tent or when sitting outside in the summer with no lights and you decide it’s just a little too dark 
If I’m outside and walking around I’ll use more than a sub-lumen level. I’m I’m not moving or if I’m in the house sub-lumen is fine.
As long as a light has 1 or 2 lumen having .2 or something like that is just a bonus but I can leave without it.
I use low-lumen lighting every day. I have a number of lights set up in my cramped studio apartment that help me move around without banging into things in the dark. Beyond the benefits of not waking my wife up by flicking on the lights on my way to the bathroom at night, it’s also nice to not have to seer out my own eyeballs by turning on the overheads once I get there. There are lots of ways that kind of low light level can be useful. Coincidentally I just put together an article today about how I use these lights around my apartment .
All of these lights include or are entirely built around a patented technique that we developed called Low Glow that lets us run LEDs at low current for long periods of time while still producing useful light. Very similar to a flashlight’s moonlight mode. With my 27-year-old eyes the light produced seems fairly bright, offering enough to usefully illuminate my entire bathroom with just one repurposed Deck Marker Light, but even my grandparents use our Mini LED Guide Lights and find them bright enough to be very helpful.
I use moonlight mode almost every night. When i go bed too late and somebody is already sleeping or also with tailstanding light to move around a room without disturbing anyone (a week ago i used programmable akoray, now i’m using a V11R).
I also like 3 lumen mode (like the one of thunite Ti) to go out when i don’t need a wall of light or, like foy said, for job that don’t want light reflection.
SC51 at LOW1 or LOW2 all nights as a nightlight.
Ridiculous runtime, if used some 6-8h a day…
Like others have stated….either .09L or .5L every night (check on the kids, dog, bathroom, whatnot…)
I use moonlight/firefly mode pretty much every day after I got the firefly version of the ThruNite Ti. Some may think that 0.04 lumen is useless, however due to the light having a reflector I actually find it is enough to be useful even when not in complete darkness. Sure, it won’t light up anything further than approx. 6 feet in firefly mode in total darkness (this is based on my eyesight), but if needed you can always use the high mode.
I keep a light on moonlight mode while tail standing every night so I can find it if the power goes out.
Walking around is easy with moonlight too. My zebralight will light up the whole bathroom when tail standing and if I have dark adjusted eyes.
+1 moonlight mode. Its a flashaholics paradise here, well i think so anyway 
very dark on these cloudy nights, almost pitch black, the nearest street light is half a mile away but might as well be in the next county for what good it does. So a Xml driven at just 3ma is suprisingly adequate for moving around the house or reading once ones eyes are adjusted. Someone on here said 3ma is about 1lumen, i cannot believe the efficency of these led’s, a year and a half ago i would have laughed at the suggestion of usable light from so little current, simply amazing. On most of the time its not worth the effort of switching off and is easier to find if mislaid. I prefer plenty of lumens outside tho, some sheep got eaten next door and i like to know whats out there watching me in the darkness.
I use the moonlight modes on my E1320 lights every night when going to the bathroom, when looking for something on my night stand or when doing anything late at night. I have my 5 E1320 lights scattered all over the house -- ALL in moonlight mode. All of my other manafont and deal extreme lights have special jobs as permanent dust collectors.
I’d use moonlight on every night of every backpacking trip if I had a moonlight mode. As is, I have to shield the vast majority of the 7 lumens that comes out of my headlight or dx coin light because that much light is blinding when trying to read in a bivy.
ThruNite Ti - 0.04 lumens, somewhat throwy beam
ThruNite T10 - 0.09 lumens, somewhat throwy beam, tighter than Ti
ThruNite T30 - 0.09 lumens, throwy beam
Spark SD6-500 - 0.5 lumens, pure flood or somewhat throwy beam (optional reflector)
4Sevens Quark 123T - 0.2 lumens, somewhat throwy beam
HDS Ra Clicky 120T with a Nichia 219 swap, set to start on the lowest low, probably puts out 0.01 somewhat throwy lumens
Four different QTC Peaks, all can put out so little lumens that you can see the lines on the die with dark adjusted eyes, usually set to 0.05-ish lumens when I use them
I use these lights, mostly the Ti and/or T10, every morning making my way out the door to go to work. I used to use 3 lumens, but, I was waking up everyone when I did. I don’t use the 3 lumens low anymore.
Almost everynight.
Indoors it is great if you just want to get from one room to another, or find somthing in a drawer.
I either turn on my SE-1 while it's clipped in my pocket or I cover the lens with my finger to achieve a dim illumination .
I'm too lazy to hunt for modes ...
Like everyone else, I use mine to get around in the middle of the night. I ceiling bounce my zebras on lowest to get dressed in the morning so I don’t disturb my sweetie. They are perfect in the bathroom so I don’t destroy my night vision and can fall immediately back to sleep.