Agree with Steve. I am only up to about four reloads per case using the XDie but cases stay as set by the die.
I have no idea why the instructions say to trim to 0.020" less than max length as that is usually 0.010" less than normal trim to length. You adjust the Xdie to match the trim length so it should not matter what length that is.
I initially trimmed to 1.740" but after a while saw no need and now trim to 1.750" and readjusted the Xdie to match.
Do a web search and you will find a couple of articles where guys did extensive testing and gave up after 20 reloads with no sign of case failure.
I also use Xdies for .308 and .30-06. Shoot in AR15s, Garands, and PTR91 no issues.