[DougofTheAbaci]

By design, perhaps - HD600 pads are known to have a relatively shorter service life. Ditto the K701/2, whose pads have the shape that adds toe-in to the drivers (vs the mount on, say, the newer headphones like the HD800 and T1). I'm not about to spend on the HE500 and a proper amp for it  just for cheaper pads either.

There's also the possibility that you might not be noticing the effects the on the sound as much as I do, even if the wear on the pads puts their cups at comparative distance from our ears (note that when I stop using HD600 pads it's not like they already look the part, like I've worn them for a week straight and will never go back from that compressed shape). The wear on the HD600 pads makes for sharper treble and mudslide-like bass and bass drum notes. If your music doesn't have such notes, particularly with the bass, then this is hard to notice even on an HD600. Vocal tracks for one unless they have high pitch sections don't sound different.

A better suggestion is find a pair of headphones that don't kill the cups every few months. Seems like a great way to waste money. I have a spare set of HE-500 pleather pads (the velours are too itchy for my tastes) and the ones I'm wearing are virtually identical. I've had them for at least a year and a half so... Yeah. Read that as you will.

 

[ProtegeManiac]

A better suggestion is find a pair of headphones that don't kill the cups every few months. Seems like a great way to waste money. I have a spare set of HE-500 pleather pads (the velours are too itchy for my tastes) and the ones I'm wearing are virtually identical. I've had them for at least a year and a half so... Yeah. Read that as you will.

 
Which is what I did, as related to my reasoning in my first reply to your post, although what I did was to get a headset that takes generic earpads from random electronics stores here, instead of spending more on the HE500 and its amp to skimp on earpads. Because of this I no longer need to use the HD600s for several hours, usually at the hottest parts of the day (since the only person I know personally who plays TW lives in a different time zone), and on top of the decreased wear I'm swapping out two pairs of pads (I got a third pair before I totally wore out the second) every few weeks. Now I can wash them anytime and have a spare pair lying around, and it's been a year and even the older pair doesn't suffer any deterioration in sound unless I wear them for hours several days straight. Best of all the headset is the same price as the earpads, and personally I'm too busy directing troops or fragging people to notice the difference in SQ anyway. An explosion or crashing cavalry sounds the same to me if my brain is preoccupied. Movies though are another matter entirely, as similar sound effects are noticeably better on the HD600 since I'm not preoccupied with mission objectives.