Paper vs. Trons

This whole discussion of the durability of electronic media has gotten me to
thinking.

These days, I very rarely buy paper books anymore. My last three Harry
Turtledove books and my last Stephen Donaldson book were bought from eReader
in electronic form only, even though in each case I have the first books of
the series in paper (hardback). Logically, I should have bought the hardback
books to complete my paper collection. Why didn't I?

In a word - space! I've never counted the books I have, but they run in the
thousands and they take up a LOT OF SPACE. I live in a small house (1600 sf)
and don't plan on moving anytime soon. I just don't have space for more
books.

Also there's portability. It's much easier to read an ebook while in line at
the commissary than a paper one. I carry about 100 books on both of my PDA's
and I can read any of them at any time, anywhere. Can't do that with paper!

I never really thought about the durability, mainly because I have so many
backups and I figure I'll always have something to read them on. If worse
comes to worse, I could just keep one of my current PDAs when I next upgrade
either of them, so I'll always know I have something to read my current
collection on.

I feel pretty comfortable that eReader books will be useable for many, many
years to come. I don't know that any of the major ebook formats have changed
any so that a five or six year old device couldn't read them. (And I really
don't know, except for eReader, which I know hasn't changed in years since
I've still got books from my Palm V days I can read).

So, is there really any reason to be concerened with the durability of ebook
formats?