What "preservative" can I add to cookies & bars to keep fresh longer? Even well wrapped, freezing takes away that "fresh-baked" taste.

Add about a tablespoon of corn syrup to the dough along with the sugar at the step where you are creaming together the butter and sugar. Also, you might try either rolling some of your dough into a log or scooping it onto a baking sheet, then freezing the unbaked dough. That way you can pull out what you want and/or need, let them thaw, then bake them fresh on the spot