So far, they have been great. No contact with the driveshaft, no leaks, no CELs. I wish I could tell you how many miles I have put on them, but I'm really not sure. But they were on the Jeep for my last big trip - Chicago to the Rubicon and back again, so 4000 hard, high speed miles, plus across the 'con. I don't think I could be much harder on them then that! lol. They must have at least 10k miles on them by now, including that trip. Everything else has just been daily driving, but they are doing fine.