i did a little test with 6tcu cases in my contender. i fired, and refired the same 20 cases over and over about 8 times. i resized the first firings without bumping shoulders back. on about the 7th firing of the case, misfires showed up. retried, and it got worse(multiple misfires out of the 20 cases). so.........i bumped the shoulder back slightly to match the barrel to frame gap. misfires imediately disappeared.
it took that many firings before the cases lengthened enough from head to shoulder to cause the misfires. so...............if a guy has 100 pieces of brass, it could take up to 700-800 rounds before the misfires start showing up. that is considering if you rotate thru all the 100 cases before starting over.