Great work, Tyll, Arnaud, and anyone else that helped too!
It seems you are nearing the limits of what you can do with your equipment and setup - the dedication to do this is incredible. The results are great, too. At least as many questions were answered as raised - a good thing, I think.
Great control for the ear pads - that's one of the things that has been thrown around here by myself and others as a very real change that hasn't been controlled for yet. I don't think anyone's made measurements yet, though. I don't know about the Q701, but the HD 600 pads wear down very considerably over time (depending on the clamping force of course). Not saying I expect you to measure a well-worn set of pads compared to new ones, but you know, if you get bored...
The first thing I can think of that would have been interesting to do with the same setup that you had is leave the headphones on when you were done, and wait a whole test period of 331 hours - then do the whole thing over again (or at least the start of it). Another one of the loose ends that has been mentioned here is driver suspensions returning to their original state after use.
Edited by BlackbeardBen - 1/7/12 at 9:15pm