Originally Posted by Pleiades

That sounds about normal, well for me anyway. I always used to pack them out when I changed the rear tyre, then replace them the next. So effectively they lasted two rear tyres worth of mileage - anywhere between 5000 and 7500 miles on average.

Best thing you can do is swap them for some polyurethane ones which can be obtained from Hunday on this forum. I have these now and they're still as good as they day they were installed 10K+ miles ago.

http://www.xt660.com/showthread.php?t=21410

You could also do the bearing mod too, but as yet I personally haven't found that necessary to do.