We have seen problems with both the sway bar link bushings, and the a-arm bushings. As John indicated I think a lot of the problem is the leveling of the coach as it causes the coach suspension to remain in a significantly different position the ride height. We have replaced quite a few a-arm bushings that were very cracked and damaged on the outer edge. When it is removed the bushing was still in reasonably good shape in the area that supports the suspension. I think that they should be replaced when you hear creaking or have an alignment issue. The sway bar bushings are a different story. If you look at the bushings with the coach dropped in the front (sitting on the stops in the bags) the links are pulled causing a significant load on the bushing. Over time this will cause even the harder urethane bushings to fail quickly. Having said that, as indicated they are easy to replace, and very inexpensive. We have seen coaches that have been run many miles with the bushings missing (sway bar links) and it does not appear to do any damage to the components.