  In this multi-instrument paper, we search for evidence of sustained magnetic
reconnection far beyond the impulsive phase of the X8.2-class solar flare on
2017 September 10. Using Hinode/EIS, CoMP, SDO/AIA, K-Cor, Hinode/XRT, RHESSI,
and IRIS, we study the late-stage evolution of the flare dynamics and topology,
comparing signatures of reconnection with those expected from the standard
solar flare model. Examining previously unpublished EIS data, we present the
evolution of non-thermal velocity and temperature within the famous plasma
sheet structure, for the first four hours of the flare's duration. On even
longer time scales, we use Differential Emission Measures and polarization data
to study the longevity of the flare's plasma sheet and cusp structure,
discovering that the plasma sheet is still visible in CoMP linear polarization
observations on 2017 September 11, long after its last appearance in EUV. We
deduce that magnetic reconnection of some form is still ongoing at this time -
27 hours after flare onset.
