I apologize for leaving you with an open box of dry pudding, but I'm sure it will come in handy for a future cake. I keep pudding mix around for various recipes and it stays fresh for a while. Plus it only costs about a dollar. I like the flavor of the pudding mix and the way it softens the cake a bit. I'm not sure what would happen if you left it out and just added more lemon flavoring. There are probably ways around it, but I recommend using the pudding mix before making changes.