The mid-infrared (mid-IR) range offers an obvious and advantageous choice in following the late-time evolution of supernovae (SNe). First, the peaks of their spectral energy distributions (SED) shift toward the IR after the photospheric phase; second, mid-IR observations are practically free of interstellar extinction, which is also an important factor in following distant, continually fading objects. Moreover, special astrophysical processes can be traced with mid-IR observations including dust formation, as well as interaction between the SN ejecta and the circumstellar matter (CSM). Recently, the Spitzer Space Telescope has been the most essential tool to detect mid-IR radiation of SNe and to follow the years-long evolution of these objects. Based on the results of a comprehensive analysis of far the largest mid-IR dataset of SNe ever studied (Spitzer/IRAC data of ~1100 SN sites including 120 positive detections) [1] as well as on that of previous studies, we present an overview of the "SN Legacy" we have from Spitzer observations, and the way how it can help in preparing for the upcoming era of infrared SN research. [1] Szalai T. et al., 2019, ApJ Suppl. Ser., 241, 38