I haven't tried this (yet) but recently read that a jack-o-lantern will last much longer if you coat the cut edges with petroleum jelly.
Oh, and thanks to the costume swap hack, my almost two y.o. has his choice between a lion and a dinosaur. I'm going as a witch (thanks to the Goodwill) so if i can talk my husband into a wardrobe costume (?) we'll have the Narnia Chronicles down pat. Happy Halloween!
More: Halloween hacks