I'm fairly sure I heard a difference around 20hrs.
The highs seemed to mellow out a bit. At that time I really began to notice how clean they sounded.
It could be that I hadn't really turned them up until around that time.
I listened an hour here and an hour there. They were never on without me listening in those first +/-20 hours.
It could have been me, their position, any number of things really.
It did happen while I was listening. All of a sudden its like they relaxed.
Up till that time I wasn't sure I'd made the right decision. All smiles since.
Living on the iPad these days.