Varies. Typically a warm-up takes 15min and a burn in takes 100 hours.

It might be drawing the 310W when playing under full load but you’re right that a significant amount of power is drawn at idle for class A

I mostly listen to Asian vocals.

Best headphones are the Hifiman Susvaras driven by the Benchmark HPA4 or the Holo Bliss

Best iem is the Sony JustEars driven by a Cayin n6ii with the r2r module

Frequently stores have many demo sets for headphones and iems to try out. They also provide players and I stream from Tidal or bring my own source.

The professional recoding was already mastered like this. Very bad compressions and overblown drums and this might be the original intention of their record company, since it takes a special effort to do it this way.

What you can probably do in the meantime is find live performance recordings and strip it down, or just play those live versions since they tend to be more atmospheric.

Yes I just get really tired and it feels like there’s something pressing against your eardrums. I had these issues with the Sony xm3 and 4 headphones. However I do not have the same issues with their iems.