The funny part is that the older 'f/s' designation means Field Serviceable, but I've never ever needed to, even after years of use.
The only trouble I have ever had out of any AT Headphones I have owned is their ear cup cushions, I ware out 2 sets in a year, and I have 3 pairs of ATH's! They start flaking....basically disintegrating. This is on the "high-end" ones & my 2 pairs of cheapo closed back ones for tracking & practicing!
The M40fs/ and M40x also came with 3 cables that attached to the phones themselves, straight, coiled, and a straight-coiled one, all about 6' in length, but none of these ever went out on me.
And I never purposely collapse my phones, taking them off, then picking them up causes the cups to either fold inward, or collapse like you are placing them in storage....VERY aggravating when this happens every other time you pick them up in a session!
I solved this on one pair by wrapping a piece of gaffers tape around the joint where they fold. If you have long hair that is a pain, and if you have short hair it seems to really hold the heat from your head, creating a hot spot above each cup section...I am looking into a small drill bit & screw, but with my luck I will drill thru the driver!