"Loud" is a bit subjective, but in my experience most people make their volume far too loud. Even moreso if you're attempting to overcome the background sound around you.

The articles below discuss both volume and duration. It's also worth checking out the OSHA guidelines which pretty cleanly show the relationship between duration and volume. (ie, "safer" volumes still cause damage with enough duration.)

https://health.clevelandclinic.org/how-to-rock-out-with-ear-...

https://healthcare.utah.edu/healthfeed/2024/01/listen-headph...

https://www.cnet.com/health/wearing-headphones-right-now-fol...

https://www.cdc.gov/niosh/noise/prevent/understand.html