When is it right to kill off a character?

I think about this a lot. So now I'm going to talk too much. 

So, Unqualified Death Philosophy 101. 

Obi-Wan's death is a good example of "death via natural character arc."

Just after WWII a lot of "realist" writers began to really promote the Classical Greek idea of a "needless death," and that's a trend that's continued into a lot of writing today (George R.R. Martin is super-fond of this). But I really believe "needless death" is not actually realistic. All deaths have reasons and arcs behind them. We die because of a logical series of events, either through a natural progression of a disease we picked up, or through choices we and others make--not necessarily bad choices, either. Death is a natural progression in a story, and shouldn't be shoved in just for the sake of death's impact (eg, hopelessness, emotional pull, loss, all the stuff that comes with death). We never "randomly" die, and we don't die just for the sake of death. Even if I walk under a book shelf and a vase randomly falls on my head to kill me, in real life there was a progression before the vase, a story, a series of "butterfly wing flaps" that put the vase exactly where it was, a cause and effect: even if in my limited experience I don't KNOW the cause and effect, it's still there.

"Okay, duh, a death needs cause/effect plot and all that." But I'm actually not talking about plot. That's just the surface. I'm actually talking about character development. Maybe I'm full of it and this is bullpoop, but I'm a firm believer that a character dies in a story when he's thematically "ready." That doesn't mean that he necessarily feels ready, or even expects death, but either he's finished his emotional journey, or he's embarking on a new emotional journey in the memory of another character impacted by the death. I say it that way on purpose, instead of saying he's triggering someone else's emotional journey: a dead character is still a character, and remembering that helps us avoid turning our characters into plot points and killing them off just for the sake of moving other characters along (eg., Woman in a Refrigerator Trope). I'd almost ask: "is it in this character's best interest, not as a person but as a character, to die?"

That's a weird question, 'cause we think it's never in someone's best interest to die, but for a character arc it really can be. Putting a villain to rest is often in his best interest as a character arc, to finalize his emotional story and personal tragedy; a sacrificial death is often in a character's best interest to solve the struggles he's worked through and to highlight his triumph above his own self-interest; the tragic death of an innocent can be in a character's best interest to give him immortality in the other characters' minds, and to give him a strength he never had in life.

So, perhaps look at what's in the character's best interest emotionally, and don't just look at what the death will do to other characters. Forget your big story as a whole for a moment, perhaps. Each character, even minor characters, are protagonists in their side stories, even if the reader doesn't see it, so death should be a major point in THAT CHARACTER's story, not just because of what it does to the MC or the overall plot, but because it individually advances the minor character's theme. Does your character's emotional arc wrap up well with death? How will he, as a dead character, continue to work in the story (absence is a way to work in a story!), and is that future post-death existence a natural and logical answer to his pre-death existence?

That may make no sense whatsoever, but that's how I decide character deaths. Death is punctuation--it's the period after a fully-realized life sentence, or it's the dash that drives a character's impact into the next scene.

Okay, Imma shut up now. As always, ignore me if that's useless information for you, and thanks for letting me share!