The answer is different for every person. Of course it depends on your speed,
and how often you stop along the way.
At 10 MPH, the 70 mile route would take 7 hours. More seasoned riders could do this in one day, while a more comfortable pace would be spread over two or even three days.
If you are accustomed to riding on paved surfaces, note that you can expect slightly slower speeds on this mostly unpaved trail surface.
Only a small portion of the D&R is paved, in the Trenton area.
Try the
D&R Canal Timeline Tool to see your expected travel time,
and expected arrival times at towns along the way.