The designers at Sony were right in allowing such a tiny amount of memory to the reader. You can not use it all between visits at the computer. Personally the most I used the reader before going back to check on emails was around 8-10 hours readtime. That was roughly half a megabyte of data.
Having one's collection on a card slows the device needlessly. I can only consider it for long travel periods. Going away for two years might warrant it!

I know there is a certain anxiousness in preparing a collection for format, and that there is fun in anticipation of the next book to read but it can all be accomplished with a simple reading plan. Then, as the time comes, at the same email visit with the computer, the upload is done.
Preparing books is a pleasure, not a chore to be done with.
Believe it or not, I have fewer than 10 books at a time on the reader, making it much faster in operation. Try it. Empty the reader, install only one book, you will feel a slight difference in operation. Of course if you read a different book only to suit your present mood, a wide selection is adequate but how many moods can one go through between stints at the computer?
There is more enjoyment of life through the application of patience. At first it looks more like discipline but the pleasure brought forth quickly dictates the habits of slowing down and setting to the reading inspired by an author.