The finite-difference time-domain (FDTD) approach is now widely used to simulate the expected performance of photonic crystal, plasmonic, and other nanophotonic devices. Unfortunately, given the computational demands of full 3-D simulations, researchers can seldom bring this modeling tool to bear on more than a few isolated design points. Thus 3-D FDTD -- as it stands now -- is merely a verification rather than a design optimization tool. Over the long term, continuing improvements in available computing power can be expected to bring structures of current interest within general reach. In the meantime, however, many researchers appear to be exploring alternative modeling techniques, trading off flexibility of approach in return for more rapid turnaround on the devices of specific interest to them. In contrast, we are trying to improve the efficiency of 3-D FDTD by reducing its computational expense without sacrificing accuracy. We believe that these two approaches are completely complementary because even with vast amounts of computational power, any real-world system will still require a modular approach to modeling, spanning from the nanometer to the millimeter scale or beyond.