My main concern with ebooks is preserving the books and my annotations for the rest of my life, at least. The former seems easy (I assume I can get DRM-free boo

My main concern with ebooks is preserving the books and my annotations for the rest of my life, at least. The former seems easy (I assume I can get DRM-free books easily enough?), but is there a platform-independent format for the annoations, and one that I can depend on being readable, or at least convertable to a newer format, in 30 years?