Elaine - from West Grove, PA
You can really make your favors as far in advance as you'd like. The wonderful thing about royal icing decorations is they will dry hard and keep for years. Just remember, royal icing will take at least 24 hours to dry, so give yourself enough time for them to harden completely. Once dry, they can be stored in an air tight container.
The jelly bean is going to be the deciding factor here. Don't make the favors so far in advance that the jelly bean is going to be hard and stale.