Just to pick up on this comment, my Sennheiser MM 550-X over ears are now about 18months old and done a heap of work. When I first bought them, possibly the only negative I had was the ear cushions could have been a bit larger diameter to sit fully around the ears rather than on them (I find placing the backs of the ears in the cushion and let the fronts rest on the ear is the most comfortable), but of late I am noticing the cushions have deflated slightly.......only very marginally mind you, but it does tend to accentuate this small shortcoming of the original design. I still rave about these though, they were a great investment and the various 'toys' which came with them, like talk-through, have become almost indispensable. I tried on the Parrot Zik originals at an airport somewhere and the ear cushions were perfect, so I was a bit disappointed when the 2.0s arrived in the post, to find that the cushions are smaller and very similar now to the MM550s.
I think the comfort of wearing any headphone has shot to No.1 in my book. For flights of many hours duration, it is a very important consideration.