We have an S4 that we picked up used a few years ago, and immediately replaced the power bands. Is it the only ski-related exercise you should do? No, of course not. But it is something "different" and IMHO does give you some muscle memory off-season. The one you have pictured looks very old, as it has the short bands (newer one double back and so are twice as long). Stay far away from that one. If you really want one, look for at least an S4, and as someone mentioned above, make sure it has the serial number on it. BTW, band warranty is two years. The reason they want you to replace them is they are made of rubber, and between usage and the rubber aging, that's a safe time period for them. Can you use them beyond two years? Probably, just like you can eat food beyond the "best by" date, or use bindings beyond when they are no longer indemnified. It's just at your own risk.
You can go to the website and scroll down to find "used machines"