I changed it at about 23,000 or 24,000 and never lubed it. It really isn't in bad shape now and I have it hanging on the shed wall with the sprockets. Rear shows no visible wear and the front only slight wear. This is also why I think lube may actually serve to attract abrasive dirt and shorten the life of an Xring.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!