We've got us a new thing called 'shelving'. Check it out.
Addendum GET: There really wasn't much clarification on what you were supposed to do with your old characters, but now there is. It has been added to the Shelving rules thread, and posted below for your convenience (or laziness):

Quote ()

As for your original characters that are being shelved, do this: Copy the information out of your signature, code and all, and post it in your Navi's profile. You can save the info elsewhere if you like, but what sits in your Navi's profile is the official record of what your Navi had before he/she was shelved.