I tried keeping track of number of times a 9mm case had been fired, but gave up quickly. My SR9 has close to 10,000 rounds fired and I've used the same can of brass over and over. When I shoot, I wait until I have a decent amount to clean and once clean I dump them back into the same can and when I reload them, I just grab em off the top. The ones I toss are normally user error caused, I can remember only a couple that have split. I use the same process for all other calibers I load also. Similar experience with 45 cases, but more split cases with 38spc. As others have stated, they split from the crimp down. I get the shortest life from 357, but my 357 are all magnum loads and the brass takes a beating. I shoot steel a lot and nothing sounds sweeter than the ringing of the steel when a 158gr bullet slams it hard.