I purchased 1984 on my Kindle back in March, and I always leave wireless turned off except for when I want to purchase another book. As ErikZ mentioned, it extends the battery life for weeks. I fully expected 1984 to be deleted from my Kindle once I turned wireless back on and purchased another book, but it's still there (I reopened it to make sure it was still readable as well), and I received a refund for the purchase as well. The book is also still there on my iPhone Kindle app. So maybe leaving your wireless turned off can prevent Amazon from remotely deleting your purchases? Doesn't seem likely that they would have left that kind of hole in their kill switch, but it did the trick this time.