Food plots remain essential as the late-season insurance that activates once acorns are gone, typically by mid-to-late December. Brassicas in particular peak in nutritional pull AFTER first frost, which often coincides with the end of available mast.
Real strategy in a heavy mast year: hunt mast in October and early November, hunt food plots in late November and December. State mast reports show the year's picture; crop calendar pages show the food-plot timing.