Douglas, as you have no doubt found, there is a lot of conflicting and even superstitious information out there on reloading. Generally speaking, as long as the primers haven't been stored in high temperature or high humidity, they will last a long, long time and give consistent results. My experience has been that using Cheddite, Remington, and W-W primers, there is usually miniscule difference in pressure and velocity between them. No experience with Herter's, CCI, or Federal, as they are rarely available in my area (Southeast U.S.). Good news is that Cheddite has remained commonly available, and the situation with W-W is improving.