User blog comment:Timeoin/Ask Us Anything - Variety Pack 8/@comment-94.202.243.103-20131012114654/@comment-5469467-20131013010309

Are you talking about Skyrim or Online?

If you mean Skyrim, I'm pretty sure dropping items in some places will make them disappear. In houses (especially ones you own) and possibly cities it should be fine, but in the wilderness and dungeons isn't such a great idea.

And killing a non-essential character means they will be gone forever. Since you're on PS3, you won't have access to the command console in order to respawn them.