If it sounds fatiguing and is not normally, then it is probably too loud.
If its not too loud but still causes fatigue and the desire to stop listening, then there are probably things happening in the reproduction that are not desirable and things will sound better at reasonable volumes if the problems are addressed.
Obviously louder is harder on the ears in general, but I would not be prepared to make any judgements about any particular volume being inherently better sounding than another.
I would say that having a naturally quiet listening room is of clear benefit in regards to being able to listen at lower volume without distraction or other external noises infringing into the listening experience.
If its not too loud but still causes fatigue and the desire to stop listening, then there are probably things happening in the reproduction that are not desirable and things will sound better at reasonable volumes if the problems are addressed.
Obviously louder is harder on the ears in general, but I would not be prepared to make any judgements about any particular volume being inherently better sounding than another.
I would say that having a naturally quiet listening room is of clear benefit in regards to being able to listen at lower volume without distraction or other external noises infringing into the listening experience.