Well..........there just doesn't seem to a consensus on this question at all........a lot of differing experiences and theories.
For the time being I think I'll just shoot them and if I get any cracked necks down the road, I'll give annealing a try. Won't have much to lose at that point as the brass will be all pretty much toast anyway, I suspect............Besides I have about 400 of these 416 cases and it's not like I need 200 rounds for my 450, nor am I likely to shoot 1000s of rounds. I suspect the 100 cases I made up will last the life of my shooting this rifle, even if I do get some cracked necks.