I have about 120k on the 05TB. I am on the 3rd set of Bilsteins now and they only seems to last about 40k before they loose their perforamnce. I am curious about springs and the lifespan. Truck sits fine but lately going over modrate bumps int he michigna roads, I have noticed it sounds like running over a log and bottoming out. All new ball joints ties rods, links etc. Only thing is springs or perhaps control arms giving way? I am going to replace the bilsteins again(for free) but do not know if the springs have exhausted their life. The steering is tight and performs well on highway, but when the bump comes it is terrible sounding!