The idea here is that you probably don’t have a place in your home or office where you store the shells from every peanut you ever ate. If you did, you’d definitely want to organize them by the year in which you ate them, perhaps keeping separate jars per-month or per-location where you ate the nut. You know. For posterity.
But you don’t do that. It would be insane. Once you eat the peanut, the job of the shell is done. So lose it. Ditto dead email. Never organize what you can simply discard; and if you can’t discard it, throw it onto one big pile.

On Peanut Shells and Email Archiving | 43 Folders