I had this issue when I first got mine, seal was very finnicky. Also the drivers pressed on the outer concha (antihelix) part of my ears which became very painful after a few minutes. I swapped to the angled oval Brainwavz pads, the PU leather version. Not only does the memory foam seal very reliably, including with my glasses on, but the angled shape got the drivers off of my ears so the upgrade in comfort was huge.
To be honest I didn't use them for many hours with the stock pads because it was too painful but I can say that they sound great with the angled pads, and after swapping I did not notice any large change in the character of the sound quality. Still that terrific Harman tuning that I love about them. It definitely didn't cause some ridiculous boost to the low end like I see on some of these graphs. Whatever the difference is, it's mostly unnoticeable to me.