Rivnuts from Homestead, PA on 1/24/2020 11:07:59 PM:
The terrain is not an issue as that segment is virtually flat. Weather conditions, notably rain before or on that day would influence the effort and enjoyment required over that last 73 miles.
While I don't know what your previous day's plan/mileage, you could consider going on to Whites Ferry/Leesburg to spend the night. In doing so, your final day into DC would be a short 35 miles. If you have flexibility you could make that decision at the time based on the weather and your condition near the end of your trip.
Note if you stay in Leesburg, you can normally get a shuttle from Whites Ferry to/from the hotel in Leesburg,