DIANNE - from pietermaritzbur, south africa
A lot of this depends on how you store the cakes after they are baked. Bake layers in advance, wrap well, and freeze until you are ready to decorate, and decorate as close as you can to when the cake will be served.
Oil-based cakes, especially chocolate cakes, tend to be more moist than butter based cakes. If you are worried about the cake drying out, you can brush the layers with simple syrup, too.