It depends on the weight distribution though. Even heavy headphones can be comfortable if the head wrap and ear pieces are wide and well padded. And at least on my HD 280's the thing that starts giving the most discomfort is the pressure they put on your ears (most likely intended to keep the outside noise down).
Need to give those HE-400s a look though. Have hifiman's earbuds already and I'm quite fond of the brand.