I have what might as well be a brand new 600XL mint in box, still it's natural white as if being opened for the first time 30 years ago. Still wrapped in the plastic, too. I haven't tested it out yet because I actually don't have a TV it can hook into, so I may do a video when I finally do of what that'll be like.
That said, I'm more curious about how long the 5.25 disks last. I picked up a collectors edition of H2G2 with all the nifty swag included, and again, until I get everything hooked up, I have no way of knowing. But if it (the disk) doesn't work, I still have my precious relic anyhow.