I am sorry if I took your words without citation (plagiarism .) I would only have done that sub consciously, your thoughts must have been- as they say today- impactful!
I owned the AKG K701 but they got stolen from me in a divorce. I actually like the crystalline, holographic, analytic, clear clean and transparent treble, that seems to annoy so many. My JM Focal Electras were that way , and needed the right tube monobloc amps to make them sing. .
I think the vast majority of burn in change happens relatively early. After 100 hours I tend to think it's mostly over with. Yes it seems that things get better over the long run but I am usually tweaking my system and don't know if it is the tweak, burn in or some other source at work.
I own the 7XXs and the HD 700 Sennheisers, I favor the Senns most of the time, but I still use the AKGs often enough that I am not selling them. Can't say the same for my relatively inexpensive Beyer 770 Pro 32 Ohm. I guess I should sell them but what can I realistically think I can get for them? Not a lot of dinero, so going through with a sale and the potentially psychotic obsessive buyer keeps me from selling..
I prolly should sell some of my small signal tubes. I have a ridiculous number of them.