One thing you need to understand about shears, almost everything on them is a wear item. When I worked large demo projects, we had 2 welders for roughly 25 machines. They spent every night welding on something, or replacing blades. Every two weeks they made sure to go over each attachment, be it grapple, or shear. Always checking for cracks, repairing the little cracks before they got big. Adding wear metal to the shears. A few times a year a manufacturers rep would come out and go over things as well. He would also assist with major repairs. Your biggest ally is and educated operator who knows what to watch for. Go over things with the guys, let them know what to look out for, and catch it before its a major issue.