How loud are you typically listening?

I sit 8' from my speakers in a mid-sized room with good treatments.
I like to start at 55db-per the iPhone app meter- and top out at 70 db.
Mean being 68db.  If something can't sound good at these levels
it is out. 
Each song will usually require adjusting + or- to suit me but
then again I have my "Best Of" playlist and nobody records at the
same level it seems.

I spend more time than I should with a violin screaming in my left ear.

Eh? what did you say?

120db+Great subject! I’ve played music professionally for 35 years. Madison Square Garden, etc. Stage volume frequently was at 120db, which is terrible for your ears, of course. Those highest levels were usually in big bars. I use hearing protection or in-ears to the extent possible. Cilia (the little hairs in your ear canal) die and do not regrow, back, resulting in hearing loss. My #1 tip for upcoming musicians is to protect your hearing.
That being said, most of you can probably listen louder than you are without hearing loss. You’ve paid a fortune for your systems, so use them!
Here are NOSHA’s (National Occupational Safety & Health Administration) safety standards. A shotgun is bad because your ears don’t have time to react, but your ears can handle constant noise pretty well. Charts vary, but basically, here are the standards:

90db. 8 hours
95db 4 hours
100db 2 hours
105db 1 hour
110db  30 minutes
115db 15 minutes

Remember the volume doubles every 7 db, so 95db is twice as loud as 87db. 
Protect your hearing, yes! But, if your favorite song comes on, crank it up. If you want a real movie experience, 100db peaks are no problem - as long you enjoy it. 

I’ve played more 4 hour bar gigs in the 100-120db range than you can imagine. Too frequently with no hearing protection. I’m 53 next month, and my hearing is okay - not perfect, but not too much loss in hearing tests (it’s been a while, but some high frequency 15db losses). Watching loud movies at home on your killler system is going to be fine. 

The frequency response of our ears changes with volume. Every recording has a volume it sounds best at. If you push a recording that was mixed at lower volumes it will get bright and harsh. If you play a recording mixed at high volumes at low levels it will sound dull and bass-less. I will play the record at the volume it sounds "right" at.

You NEVER want your ears to ring. Ringing indicates damage. Our ears accommodate to loud sounds but the reflex is slow which is why impulse noises like gun shots are so bad for our ears. If you are going to listen loud it is important to warm your ears up by starting at a lower volume and raising it in increments over a five to 10 minute period. I'll listen to some recordings at 95 dB. Higher than that is risky.