Yeah, it is a newby question but that's why many of us are here. It's much harder to help 'experts'!
When to anneal is one of those "this or that" questions, it's really not calibrated. And a LOT of people don't do it at all. I do, but for me it varies from 4 to 6 cycles depending on how bored I am! For sure, we should anneal the whole batch when necks start to split, OR toss 'em all out.
Annealing itself is more art than science so there's a learning curve; the difference in brass temp between too little heat to too much heat isn't much. If the brass doesn't get hot enough we haven't accomplished anything, if it gets too hot we will destroy the elastic spring back and that hurts accuracy.