to modular open design where nothing is irreplaceable.
It adds interesting aspects. For example, I work with systems that have 5 I/O modules. Each one keeps a backup of the main controller settings, so that you can replace any component, including the controller.
After a quick question on the next boot, you're up and running again.
Imagine if each module of your ebook reader had enough cheap/slow storage that everything in "main storage" could be replicated across your modules. As long as you only replace a couple of modules at a time, you'd have everything forever.