Yes, i have seen that happen on a lot of tractors. If those gears are never lubed, with automotive type of grease, and some 30W oil squirted down in there occasionally--yep--they will wear quickly, and do just that! And, they can be replaced. Study it well, and i'm sure you can do it. Thats if you aren't afraid to get dirty, or have yer knuckles nicked. If you aren't mechanically experienced, send it out!
Rusty Jones

Amazing what happen to equipment when it gets loaned out?. About 30 years ago I used sears and sawbuck cheap radial arm saw, this was after the day before I helped the guy finish off shed/pole barn style work shop. he was cutting ruff cut 4 by 4 oaks. the next day I was cutting 1/4" plywood the saw quite on the 3rd cut. But, beings I was using it at the time I called sear repair man out. $139 bucks later on a 350 dollar saw. I learned a good lesson that day? Don't borrow equipment. Knowing the day before probably what burnt the saw out. but I still didn't want that on me.

JD usually engineers there equipment pretty good, I know my LX system is rock solid with 350 hours on it, but it's not as heavy as you X500. I would say it wasn't normal for the steering to wear out that quickly. Replacement parts are probably going to be pretty high, hopfully you won't have to do it again. But, as rusti suggested some anual pre-ventive greasing sure wouldn't hurt IMO.

The part isn't too bad ~$50 for the gear and then I bought some bushings just incase there is some excess play in the steering shaft/pinion.

Hopefully the part isn't backordered..grass is still growing.