Besides not loading petal to the metal, neck sizing each time - with minimal shoulder set back (bumping) only when needed - seem to be the two factors that have given me the longest case life. Some .243 AI cases that had been fired 25 times were finally retired when their primer pockets finally got too loose. Several lots of brass for .223, .270, .308 and .30-06 are on anywhere from their 15th to 19th loading with no signs of slowing down.
And that's apparently not even pushing the limit. I've read of some reloaders who have gotten 30, 40 or more loads on their cases although I forget the details on which caliber and their load levels.
When I first started reloading and didn't know how to set a FL die properly, and FL sized every time, cases would start showing obvious signs of incipient head separation on the 4th or 5th loading.
