I think they should stay dead. It's always irked me, the furore over them dying then two minutes later, hey I'm back!
I think there is one more reason for the killing off of them which is far less noble than any others you have mentioned... Ratings/popularity. The sales for a conic when the main hero gets whacked go through the roof when they do it. What better way to reignite interest in a series.
Stay dead!!
Makes me want to kill them again and make it stick. I guess that's why the rule in killing zombies is to double tap. And yeah, I do agree that ratings play a huge factor. I don't know why I didn't mention that. Perhaps, I left it off in hopes that it would be mentioned by a Scottish gentleman in the comments section ha! There can only be so many times they could whack a character and make it come across as believable. After the 10th death, only the most foolish of readers would believe that it would stick.