I heard Jamie Ellis speak on nucs and how valuable they can be in beekeeping. He gave everyone this link.
https://edis.ifas.ufl.edu/publication/IN869 Dr. Ellis wrote this publication and it explains what a valuable asset they are and how to manage them. I know several beekeepers, myself included, that have successfully over wintered bees in nucs. I really like nucs when going into fall. If you find a weak or queenless colony they can be combined.