That's the point of DRM-free ebooks though, isn't it? You download them and keep them safe so if the provider decides to cut access to your account, you remain in possession of the goods.

So the correct advice would be to avoid anyone buying DRM-encumbered digital property - the same as RMS has been making for who knows how long!

It's safer to assume that Amazon is always acting in bad faith and search to purchase your DRM free e-books from other vendors. There's plenty of other options out there besides Amazon