3 for non-variable objects. Figure 10 shows the increases in completeness for these five and six epoch scenarios. Most of the gain for detecting variable sources comes from adding one additional epoch. The greatest astrophysical gain from two additional epochs comes from being able to better map out and subdivide the structure function by luminosity, redshift, and source type to better characterize the physics of AGN variability at these wavelengths. In particular, it would confirm the different slope of the mid-IR structure function from that observed in the optical. 

This work is based on observations made with the Spitzer Space Telescope , which is operated by the Jet Propulsion Laboratory, California Institute of the Technology under contract with the National Aeronautics and Space Administration (NASA). Support for this work was provided by NASA through award numbers 1310744 (C.S.K. and S.K.), 1314516 (M.L.N.A.) and 1317692 (H.A.S.) issued by JPL/CalTech. CSK & SK are also supported by NSF grant AST-0708082. The NDWFS and the research of A.D. and B.T.J. are supported by the National Optical Astronomy Observatory, which is operated by the Association of Uni- versities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation. Support for M.B. was provided by the W. M. Keck Foundation. 

Alard, C., & Lupton R. H., 1998, ApJ, 503, 325 

Ashby, M. L. N., et al. 2009, ApJ, 701, 428 

Assef, R. J., et al. 2010a, arXiv:1001.4529 

Assef, R. J., et al. 2010b, ApJ, 713, 970 

Barvainis, R. 1987, ApJ, 320, 537 

Becker, R. H., White, R. L., & Helfand, D. J. 1995, ApJ, 450, 559 

Brand, K. et al., 2006, ApJ, 641, 140 

Brown, M. J. I., et al. 2006, ApJ, 638, 88 

Clavel, J., Wamsteker, W., Glass, I. S., 1989, ApJ, 337, 236 

Cool, R. J., et al., 2008, ApJ, 682, 919 

## REFERENCES 

Cutri, R. M., Wisniewski, W. Z., Rieke, G. H., Lebofsky, M. J., 1985, ApJ, 296, 423 

