Not why or when, but how. I anneal the neck and shoulder of my brass with a torch every time its reloaded. I keep it simple and use a 10 mm deep well socket on a drill for 6.5 Creedmoor. I drop the case in the socket and spin it for 8 seconds in the flame of a propane torch. The socket makes holding the case easy and provides some protection for the body of the case. I think I average 40-60 rounds a week and have 200 cases in a rotation so I end up annealing 120-160 cases every three weeks. It doesn't take a lot of time, but automating the process has its allure. Does anyone have one of the automatic propane case annealers?