"Most affected by heavy loads" would be the forcing cone. They can eventually crack, but you really need to put a LOT of heavy use in for that to happen. Meaning round count above 70,000 and closer to 150,000. Very few guns will ever reach that. You could shoot once a week for ten years and hardly reach that. So shoot it and don't sweat wearing it out. Honestly most S&W and Ruger revolvers are not really broken in until you put 3000 rounds down the pipe. I know lots of guys who buy lots of guns but only shoot every other month or so. They are lucky to even ever break in their guns.