I purchased my IE8s 7 years ago and the stock cable finally started developing a fault near the connection to the right driver. IEM cables lasting 7 years with regular use during 1.5-2hr commute? Pretty impressive considering I store my IE8 by simply wrapping it around my palm and shoving it in my pant pocket along with my Cowon J3.
After a few days of wiggling the right cable around to get the sound to work, I purchased this
cheap aftermarket replacement cable (which I also spotted on ebay) hoping it would arrive before my flight back to Australia in 10 days. Shipping took only 2 days. It would have taken around 20-40 days for delivery had I purchased this from ebay in Australia. One of the perks of living in China I guess.
My first impressions after a few days of use is that for ~12AUD, the build quality isn't bad. The cable is pretty much the same thickness as the original cable, the same length, both low friction surfaces to prevent tangling, the split into left and right is in essentially the same location (very slightly lower on the aftermarket cable) and the connection to the drivers is tighter than the original cable (though the original is 7yrs old at time of comparison) so you don't need to worry about the driver randomly getting detached from the cable.
The two obvious differences between this aftermarket cable and the original is that this aftermarket cable is a lot more springy
http://i.imgur.com/7NNy449.jpg When I coil both cables around my palm and place it on the table, the stock cable will maintain its shape most of the time while the aftermarket cable springs out. When I straighten both wires, the stock cable will comply easily while the aftermarket is left with curls. Due to this characteristic, the aftermarket cable is more prone to fall into a tangle when straightening it out after pulling it out of my pocket. The other main difference is the slider adjusting the split between left and right wires is a lot more smooth on the original cable. The aftermarket cable's slider is pretty tight and will require both hands on the cable to adjust the slider as opposed to the convenience of using one hand with the stock cable.
As for the sound, I'm a cable skeptic so take that as you will.
Overall, I'd be surprised if this Chinese cheap aftermarket cable lasts anywhere near as long as the stock one but for its price, I'm pretty happy. Once again, I'm very impressed that the stock cable managed to last so long and I'll probably look into whether I can buy another one from Sennheiser when I'm back in Australia.