RCBS X-dies are supposed to greatly reduce the stretching when the expander/ball is pulled up out of the case neck.
Many people report trimming goes from every 3 reloadings to once at the beginning and it's not needed afterwards.
Reloading for a semi-auto usually means your brass won't last as long.
Reloading max, or near max, loads also shortens the life of brass.
When you trim, make sure to debur the inside and outside of the case mouth. Some trimmers (the expensive ones) do this for you but most of us have to trim, then use a deburring tool clean up the inside/outside of the case mouth to keep from scratching the bullets up during the seating step.
