Re: Case trimming- how many times?
In 1972 I got 100 17 Rem cases which have been partial neck sized and trimmed about 7-8 times each ( I have to type in a hurry because the trimming police are breaking down the door) with no case failures. In larger calibers for large game, really, really hot loads - Above max recommended -with heavy bullets may generate case failures within one to two firings. These failures typical occur in three places. Primer pockets too loose to hold a primer, split case necks, or as noted above, case head separation which is foretold by the shiny ring above the web.
Every case gets "looked" at after firing and "looked" at again before reloading. What I do is take 0000 steel wool and polish the neck with a couple of twists to clean any powder residue off it. This is a good time to look for case neck split and head separations. All of that said, the worst series of mistakes I every made was with "reduced loads" . Do not fall asleep reading that section nor forget whether you did or did not put powder in a reduced load case and charge it twice. If you do not wear glasses get some and wear them when shooting, I still have both eyes.
The Smokin Fur Rifle Club