I see you guys are still yacking about this so I'm going to throw in my 2 cents. First a disclaimer: I've been around too long to believe that things burn in or believe any of the other garbage people 'think' they hear. But.....
When the T-1 came out years ago, I bought one of the first models from Amazon. They were way more treblely sounding than my 880s. A lot of guys posted about it and sold them because of that. I remember posting complaints about the over treblely T-1s as well as the foobar EQ curve I used to tame it. Fortunately, the left driver failed within the warranty period and Beyer replaced the headphone. The new ones they sent me sounded like 650s with a rolled off high end and I posted that apparently Beyer had 'over' fixed the treble problem of the T-1 and included the foobar EQ curve I was using to boost the treble back to satisfying levels. It's been a long time now so I don't remember how long it took, but with in a short time I posted that the new T-1s with their 650 sound had reverted to the Beyer house sound and that they sounded like super 880s.
That was a long time ago but that is my recollection. I don't recall any other headphone doing that and I've never noticed anything similar from an electronic device or wire.
The other bone I have to pick is that all DACs sound the same. Years ago I took part in some double blind tests at one of the meets and I was not able to reliably tell a Stello D100 DAC from a Benchmark. However, that same Stello D100 DAC had a 192 upsample switch. When this switch was thrown, there was less bass. I didn't pursue it because it because the Stello was moved to a secondary rig, but one day I got curious and recorded the sound from the bypass position and the upsample position and ran it through the DiffMaker to see what was going on. What I heard was additional treble. The point being that although similar circuits will probably have similar sounds, different circuits may have different sounds. I noticed a similar thing with USB to SPDIF converters. The HiFace seemed to be more resolving but didn't have the 'tone' of a Blue Circle and the Peachtree X1, although resolving, sounded like a cross between the two.