Mixing volume. Your preference?

Yes.

My Apollo 16 was usually on -22dB, which is pretty moderate.   not loud, but not quiet.  But... I would listen briefly on louder and much quieter levels too  (quiet listening was always can I hear the drums and the vocal still? ok, now turn it back up).  Headphones same.  If I use VSX, it's usually only moderate volume.

I think that is a very good point. Listen at a bunch of different volumes. Kick Fletcher Munsun (sp) to the curb. At least sometimes.

Cheers,
Geoff

Here’s my take….Find your comfortable listening level when you’re playing your favorite music through your monitors. Mark that spot on your volume controller. This is where your ears like to hear/feel music. When you mix, leave the volume controller in that spot. If you have to add a limiter to your session to get up to that level then do it. That way you’re mimicking the way you like to hear music. You should be able to make an emotionally impactful mix at that level. You may have to crank it up at times to hear other details in the music, but always return to “home”. I like to turn it down relatively soft as well, but I also mark that spot as my background music listening level. I’ll even walk around my room with it low like that and clean or grab a guitar or something just to get into the same routines I would be doing with background music on in the studio. It’s all about feeling, and I don’t like to get too wrapped up in things like, my monitors must be 85dB or something like that. Actually, it turns out 85dB is around where my listening level is, but I don’t look for that number. Just the spots marked on the volume knob.

around 80db. but i turn the volume down and up from time to time and maybe mix 50:50 between one mono mixcube and my dynaudio lyd48‘s.
i attended a pro mixer and he mixed really really low for my taste all the time. he said he mixes all day long and only mixing low he can do it all day long without getting tired ears. i tried it. it was to low for me. so its really sonething very personal.

Not sure what the dB level is, but for the monitors it's not so low I have trouble hearing anything, but it's not so loud that I can't clearly hear people talking next to me.

For phones, it's about the same apparent level I guess. Not very loud but not too soft that I can't hear some things.

I mix at a conversational level and double check the mix around 85dB occasionally. I just can't mix at loud volumes for extended periods of time. I've found that if everything is clear and balanced at a very low mix volume, it usually translates to louder levels well. I tend to have to adjust the sub frequencies when playing louder. I'd also like to think I'm protecting the hearing I have left.

I’ve been experimenting with lower volume for the bulk of my mixing lately with really good results. I crank it after I’ve got everything balanced and fine tune to finish.

A few observations:
I keep an eye on the low end’s energy, but don’t obsess over it until it’s loud.

When adjusting saturation at very high levels, I don’t think I’m able to appropriately hear the differences and usually overdo it. When the volume levels come down, it sounds overcooked.

If the volume is too low, my ears strain differently and I may over-EQ or compress because I’m really just looking for more overall volume. So, finding the right low level is vital.

It seems like my reverb usage is more tasteful, I think because I’m paying more attention to the tails as the volume comes up later in the process.

My mixes are translating waaaay better on small speakers / phones, etc.

I don't mix as much on monitors anymore but when I did I went with a modified version of the Bob Katz fixed level at -23 LUFS (85 dbC, slow weighted) and adjusted for near field monitors and what was actually comfortable for my smaller room. I think that ended up being 70 dBC.

I usually listen quieter though. That's just the level to where Fletcher Munson didn't feel like an issue.

This is a good point. 
From my experience subpar acoustics can be tiring and monitoring at a lower level seems to be one way to keep some of the bad acoustic issues at bay.

I listen at a pretty moderate volume, both "just because" and also because I have to! I work at home in a converted office. It's a "treated" room, thanks to Amazon, but the combo of new speakers and a room reconfigure has meant there's a nice woofiness that pops out in the low mids when the volume gets too high. Nice. I rely on Slate VSX headphones to help me dial things in.

Just my R & D.. you can listen whatever volume you want to, on headphones or speakers. Just take a slow sin sweep 20-20k and use ProQ until the sweep is equal loudness. That will show you where the problem areas are. I like a 1-2 min sweep, followed by quicker sweeps. So NS10 (or other small monitor) super quiet + turning up a sub to assist works really well. Conversely loud you won’t need as much sub. And then of course once you know the problem areas, you can bypass the ProQ and turn off the sub, as you learn and understand what will get you in trouble. Same with headphones. This actually flattens to your own hearing issues as well, so there’s that.