I have been annealing nickel 300wsm brass for about two years. Prior to that I had 8 reloads on original loaded factory brass. All the brass is probably 8 years old. No problems yet.
I used to anneal Federal Trophy Grade nickel 338WM brass, it is essentially the same as annealing normal brass, the only thing is, the nickel starts flaking off the more you anneal it.
It also scratches your dies when it flakes off. I avoid nickel cases for this reason.
It looks pretty but I'm not convicted its such a great idea to try to anneal that brass.
I have a near 50yo Herter's case trimmer and it chews the case mouth more than cuts it...it cleans up nicely but you can tell a difference when trimming cases.
I use the manual annealing method using a socket, cordless screw driver, torch and tempilaq 750. I've been reading about the molten salts method and I am very tempted to try it.