I have a QC 35, and I have experienced some of the degrading of sound isolation. After some research I discovered than the pads account for much of it, and they

I have a QC 35, and I have experienced some of the degrading of sound isolation. After some research I discovered than the pads account for much of it, and they degrade rather quickly, but not faster than any other headphone and I have very expensive headphones. My Sennheiser 650 is >400 usd and is on his third pair of pads. The QC35 is so great that I developed ear problems for using them too much. So be careful with that.