When done right, annealing extends brass life and makes neck tension more consistent, something very important for accuracy.
Annealing is a process wherein heat is applied to a metal in order to change its internal structure in such a way that the metal will become softer. “Properly” annealed cartridge cases are essential to maintaining accuracy and long case life when using hand-loaded ammunition.
Not only will annealing make the brass last up to 10 times longer, but it will tighten up those groups too.