Front Lower control arms and rear upper control arms

My X5 is a 2001, 3.0i, I have replaced the front lower control arms and the rear upper contol arms due to really bad tire wear. The truck has only 142,000 miles on it, and I changed the front lowers out on it around 60,000 miles ago, so those were shot at 80,000 miles. This doesn't seem consistent with the quality BMW trumpets, nor the mileage one should expect out of a $70,000 vehicle before replacing chassis/suspension components due to excessive wear... Is this consistent with everyone else's experience?