I had to replace my spindle bearings sooner than 500hrs (the bearings were obviously shot). It was an easy job. Remove spindles, remove retaining clips, press bearings out, replace. The bearings are cheap on Amazon. If you're going to have it apart it wouldn't hurt to change them.
Bobcat Toolcat 5610G, Deere X744, Cub Cadet IH 982
We have 525 hours on a 62c deck with no spindle problems. Last winter I lubed the idler pulley bearings with a needle grease gun adapter by carefully sneaking past the seals. The deck is slightly quieter too.