  Here we present new - and, nevertheless, last - mid-infrared (mid-IR) data
for supernovae (SNe) based on measurements with the Spitzer Space Telescope.
Comparing our recent 3.6 and 4.5 $\mu$m photometry with previously published
mid-IR and further multiwavelength datasets, we were able to draw some
conclusions about the origin and heating mechanism of the dust in these SNe or
in their environments, as well as on possible connection with circumstellar
matter (CSM) originating from pre-explosion mass-loss events in the progenitor
stars. We also present new results regarding both certain SN classes and single
objects. We highlight the mid-IR homogeneity of SNe Ia-CSM, which may be a hint
of their common progenitor type and of their basically uniform circumstellar
environments. Regarding single objects, it is worth highlighting the late-time
interacting Type Ib SNe 2003gk and 2004dk, for which we present the first-ever
mid-IR data, which seem to be consistent with clues of ongoing CSM interaction
detected in other wavelength ranges. Our current study suggests that long-term
mid-IR follow-up observations play a key role in a better understanding of both
pre- and post-explosion processes in SNe and their environments. While Spitzer
is not available any more, the expected unique data from the James Webb Space
Telescope, as well as long-term near-IR follow-up observations of dusty SNe,
can bring us closer to the hidden details of this topic.
