  We analyze the late time evolution of 12 supernovae (SNe) occurring over the
last ${\sim}$41 years, including nine Type IIP/L, two IIb, and one Ib/c, using
UBVR optical data from the Large Binocular Telescope (LBT) and difference
imaging. We see late time (5 to 42 years) emission from nine of the eleven Type
II SNe (eight Type IIP/L, one IIb). We consider radioactive decay,
circumstellar medium (CSM) interactions, pulsar/engine driven emission, dust
echoes, and shock perturbed binary companions as possible sources of emission.
The observed emission is most naturally explained as CSM interactions with the
normal stellar winds of red supergiants with mass loss rates in the range
$-7.9\lesssim \log_{10}(M_\odot\text{yr}{}^{-1}) \lesssim-4.8$. We also place
constraints on the presence of any shock heated binary companion to the Type
Ib/c SN 2012fh and provide progenitor photometry for the Type IIb SN 2011dh,
the only one of the six SNe with pre-explosion LBT observations where the SN
has faded sufficiently to allow the measurement. The results are consistent
with measurements from pre-explosion Hubble Space Telescope (HST) images.
