It is hard for me to let go of brass, especially if my loads are turning out good accuracy. Add to the fact that it's somewhat pricey and hard to find these days and it makes me more reluctant to toss it!
I have some .300WinMag Frontier brass (Hornady) that I have been shooting for about 8 years. I have "stepped" on it quiet a bit and shoot mostly book max or slightly above. A few years back I noticied the primer pockets getting loose so I purchased the RW Hart & Sons Case Saver. IME, it does not return it to factory tight but does give you a little more life out of your brass.
I make a small red Sharpie mark on the case belt during primer seating, if it feels looser than I think it should be. During the next prep session I look for these particular pieces and use the Case Saver on them.
I did it this way because not all the primer pockets have the same tension. It seems to be working pretty good and I have not had to re-tighten a previously tightened piece of brass.
I'm not sure this will extend the life of ones brass forever but between this and annealling I should get a little longer brass life. Happy, happy, happy!