firstshot,

It is true that you will need to bump the shoulder back from time to time when neck sizing. How often? Perhaps after about every 5 firings when neck sized. When will you know? When you try chambering a recently fired case and you noticed a little stiffness in closing the bolt. An excellent die to use for this is Redding's Body Die. This die resizes the body without touching the neck, so after using it, you must once again use your neck sizing die prior to loading. Hope that helps.

Don