Late-time (>100 day) mid-infrared (mid-IR) observations of supernovae (SNe) offer a valuable probe of their circumstellar medium (CSM).  Long after the SN radioactive tail fades, warm dust can stay bright at mid-IR wavelengths due to alternative heating mechanisms.  Already, this technique has been demonstrated with the Type IIn subclass, which we show to have large, dusty, pre-existing shells formed in pre-SN eruptions.  While other SN subclasses are thought of having relatively low density circumstellar environments, a growing number of these explosions now show evidence for extreme pre-SN mass loss and similar mid-IR characteristics.  Characterization of the various CSM environments has implications on our understanding of massive star evolution, mass loss processes, and the SN progenitor system itself.  Here I will discuss the latest mid-IR observations of different SN subclasses, the implications of these results, and what the future holds with the launch of JWST.