I've never found justifiable reason to do anything more than a very occasionaly trim to length. I know some will howl and tell me I'm crazy but it's a fact. I was always big on MAKING my own cases where possible as I had a zillion rounds of one fired /06 brass and with an RCBS file trim die I could make dang near anything. Some of my case creations I was sure when all was said and done that the case neck was a little thicker than it should be. I loaded it and shot it anyway with never any ill effects in accuracy, case life or pressure.

This is the sort of stuff that benchresters and other anal reloaders worry about at night. In reality, I believe its a non-issue and not worth the trouble to ever do.