FL sizing isnt gonna make too big of difference in case life. it is more of an issue with belted rounds, it is said that the brass thickens above the belt.. i dont have a problem with this, i fire my cases a set number of times, then load them for the last time and vaccume seal em and put them in ammo cans.
if you are not FL sizing, your right, you need to keep the brass with the gun it was fired in. if you still had problems after bottoming out the die and then + 1/4 turn, for what ever reason you may need a small base size die.