Every time something burns in, it's for the betterment to the person saying they burned their pair in.
Headphone too dark and murky? After burn-in it's so transparent!
Headphone lacking bass? After burn-in it kicked like a mule!
Headphone lacking thickness? After burn-in the instruments were so tactile!
You never, ever hear stories about the negativities of burn-in, which alone is proof of how much confirmation bias drives that myth. Fang can say the HE-560 needs 150 hours to sound its best, which is all well and good, but let's not take blow those comments out of proportion. There might be minuscule changes in the sound of the speakers, but it's certainly never anything that's magically night-and-day like half of what you read on head-fi regarding the issue. If your 560 sounds a certain way when you first get it, it will most likely sound near the exact same after 3000hours of music played through it. I know I personally won't be discrediting the opinion of any individual who wants to make remarks about the 560's sound when they first open the box and listen to them.