My point regarding having 3 years worth of reading on your device at one time is that it is ridiculously easy to always carry all the books most people will ever read in their life. And even for the people who read a lot, and/or want specific books,
and I myself am among those people, can carry a significant portion of their library on the internal storage. I for example keep my entire TBR on my Kindle, all books that I know I want to read, enough to keep me happy for a very very long time. As well as my favorites that I know I will want to re-read at random times.
I have never had to worry about not reading
that particular book because it is always available within the day -- if not on Amazon's cloud, then on my hard drive or in my Dropbox OPDS catalog.
But if it isn't, because you happen to be in the Middle Of Nowhere without your computer or access to WiFi, (not my experience but I know other people do,) then you would
still have a couple thousand books that presumably
you put on there because you want to read them next!
It isn't necessary to move your library from one device to another, either, because in case you haven't noticed, that device also has internal storage!
Where does it end? If you have 32GB of books on your nice ereader with the expansion slot, will you go into panic attacks because you can't fit another 100GB?? Maybe the book you end up wanting is the 80,001st book, the one you couldn't fit on! Oh noes!
Anyone who feels a need to download the entire Project Gutenberg and Wikipedia Just In Case, I would recommend them see a doctor, because they clearly have some kind of neurosis. Backing up your purchases is another matter, and I do do so myself. But it doesn't all need to be on your device...
And if you really need your ereader for playing music/audiobooks, then you have missed the point of an e
reader. Get a freaking MP3 player.
NOTE: In order to preempt yet more rants about why I am using the word "you" instead of "I", I would like to point out the existence of a second meaning of the word "you", which you can read about here (second definition):
http://www.merriam-webster.com/dictionary/you. I am not sure why anyone might be unaware of this... unless of course the person is just interested in stirring up trouble.