Most of the several hundred cases I have in my rotational stock dates back a couple decades or more... with some R-P cases more than 35 years old with more than 20 reloads on 'em!  I anneal every 5 or so loadings, and I neck size only.  I average a cracked neck every time I shoot (because let's face it... the brass is old).  I have some newer brass but I'm holding off on using it until my older stock is plum wore out! 

Annealing is very simple.  There are several methods and some guys swear that their process is the ONLY way to anneal.  Here's how I do it:  Using a LEE trimming shell holder chucked in my drill, I slowly spin the case while heating the neck with a butane torch.  Heat the case until the shoulder just starts to change color... but NEVER to glowing!  Then, drop them out of the shell holder into a metal bowl and let 'em cool!