I have read hundreds of books on my Kindle that I bought ages ago. It still works perfectly and battery life is still good. What's the problem?
When Amazon decides to cut you off, you’ll know. Example: bought Albums on iTunes over a decade ago. Can’t re-download. Not even for a nominal bandwidth fee.
If Amazon remotely nukes my device, I've still had it for many years working perfectly. So I'm not going to loose sleep.