The Jeep manifold is well known for it's cracking. Some are made with cast components. Cast manifolds crack a lot in many applications. Headers not much. Hot rodders, classic truckers, racers, performance vehicles and Off road all use headers without much trouble. If you live in the snow, everything rusts. Your whole car rusts. For the most part headers are not short lived. Manufactures used cast manifolds for one reason...price. Once you make the mold or die, the piece part is $1. If headers are build right of good material, they will last a long time, especially if coated. With headers you get weight reduction, HP, repairability and special fits.
