I don't know if it's because I've started to wear my HD650's for longer now - by longer I just mean 2-3 hours, but I find them really uncomfortable, to such a degree that they'll leave a mark on the top of my head. Yeah, I'm bald so I don't have natural padding either lol.
Particularly the opening in the middle of the padding does no good.
Is it possible that the padding has lost it's density somehow? I find that a bit odd.
Just for reference I'm talking about this bit...