Guffey comments on my .308 Win. case I reloaded 47 times:
A reloader fired one 308 Winchester case 47 times, I ask him the weight of the case before he started, he did not know (the weight) and he did not know why I ask the question, I did not get around to asking him the diameter of the flash hole through 47 firings, I did not ask him the diameter of the case head before and again after the test? I did not ask him the case head thickness before and again after he started his test.
I didn't care what any dimension the case was before, during or after that test except for case length. Nor did it matter to me why he asked about it. I knew it didn't make any difference as far as accuracy is concerned. Others have done the same and they didn't care either and got the same accuracy for the life of the case. The primer pocket in my case didn't open up enough to make any noticable difference in force needed to seat the primers.
Some folks reloading the same case a few to several dozen times notice the primer pocket getting too big to hold new primers. So they swage the case head back down a couple thousandths and start over with a tight primer pocket. The flash hole diameter probably gets a bit smaller, too.