How/when to check axle bolts, bushings and shackles?

I watched a fifthwheel go over a 6" curb when coming into our winter park. next season he was telling me on the trip home he had almost every suspension part broken on that side and the tires were trash. what a look on his face when I told him about the curb he drove over. claimed he felt nothing. Slow bumps are felt to me. curbs I do not hit.
chevman