I don't usually reread unless by accident although I have reread some books I read 40 years ago.
DRM is an inconvenience, but I feel that many ebooks would not be legally available without it especially library books. I also think that epub and mobi books will be readable in the forseeable future either on a reader, computer app, tablet app or downloadable from the library. (My opinion only)
DRM reassures authors and publishers in a limited sense and of course is their choice to make, just as we have the choice to buy or not buy.
With so many laws being passed to protect rights holders, which I don't disagree with, it would be nice to see a law passed that would protect buyers against obsolete formats, such as ensuring that they would have a readable copy of purchased content for say 75 years.