Amazon banned me (for something completely unrelated to Kindle books), and I lost access to everything on Kindle as a result. It's a good thing I hadn't spent much money there, and obviously I'm not buying any ebooks going forward.
Buy ebooks from Baen directly, or from Tor on your service of choice. These publishers release books DRM free, so you actually own the file. Any other ebooks you “buy”, you’re renting.
Alternatively if it's not available DRM free I'll just buy it and support the author from wherever and then pirate a DRM free copy and archive it.