I just read a great post by Brian Hailey from his Civil3D plus blog regarding adding contour data to surfaces. He has some great points. If you're like me and the rest of the Civil3D world, we tend to use the items straight out of the box. Along with that, the software works quickly and we don't take enough time to truly analyze our surfaces and ensuring triangulation. Take a look at his blog post and see test the results for your selves!!
http://civil3dplus.wordpress.com/2011/08/13/adding-contours-to-a-surface-youre-doing-it-wrong/#comment-2862
