This is something I've standardized in my life since I was maybe seventeen or so. It started one night where I sat in my room, looked up at the ceiling fan on the hot summer night and spun Emperor's "In The Nightside Eclipse" from front to back, with my cellphone off and my door locked. No movement, bathroom breaks or stimulus other than sound at all.
From that moment on I realized that all metal that is worthwhile deserves this type of isolation. There's certainly magic hidden in certain albums only accessed with a long, strong, uninterrupted attention span.
I think that the metal which requires this longer attention span is my favorite metal. I enjoy long and elaborate riffs, narrative phrasing and dynamism. Style, production quality, playing ability and dramatics is really nothing to me. I can listen to Vader and Graveland back to back with no qualms about how bad Capricornus is on the drum-kit.
When first I got into "underground" metal, I focused on all of the aforementioned qualities that I'm now currently ambivalent towards. I used love Nile, Cryptopsy, Angelcorpse and Suffocation above all else.
Throughout experience in the genre(s), my mind began to become more attuned towards the things that make metal (and music in genreal) meaningful, which is substance. If they ALSO excel in style, production, ability and dramatics... then that's just an added bonus. It tells me that they're adept in playing. Though, I'm most interested in composition.
As a result I don't hate Nile, Cryptopsy, Angelcorpse and Suffocation, I just listen to them for different, better reasons now. Not so much Nile though... maybe "Black Seeds of Vengeance" for it's riffing and "Annihilation of the Wicked" with the rhythmically thunderous parts is are the two I can pick out from their catalog. I own them all, but asking me to differentiate between the albums is nearly impossible for me at times.
Back to the subject at hand... I truly ritualize metal these days. Yesterday I listened to Samael's "Worship Him" without any interruptions in my dank, cold cellar amidst the humid weather of the early nighttime. That album wins in every way possible. It amazes me how that album effects me with an unbroken concentration.