Since I have saved just about every story I've read and gone back and reread a number of them I must say that I prefer to download to my personal archive from the ARCHIVE. The file sizes are much smaller than me have to take each chapter from here and copy it into Word to make one file and save it. Also I like the descriptions of each story.
Since I'm not a writter I guess I should express and opinion but I'm going to anyway. I agree that probably many don't read the threads. Also it is easy to forget if you've done something or not. So I would think that a nicely worded email asking an author to submit their finished story to the Archive would be appropriate. You could also mention as Tank did that it saves their work in case they have a system crash. Although to quote Clark Kent, "Don't you back-up to floppy disks." Or in this day and age CD.
Again my vote is email or at the least the comments folder.
