A lwb is really too long for a single drive shaft. The length depends on tubing diameter and thickness. Center bearings normally last a very long time. Are your joints in phase and did you change the plane of the engine or the rear. If the plane has been changed a one piece shaft will fail in no time. I am assuming you are speaking of the center bearing. The carrier bearing is actually the bearing that supports the ring gear, but the center bearing is quite often referred to as a carrier bearing.