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 73 mile route would take just over 7 hours. Experienced riders could do this in one day, but most people will spread it out over two or three days.
When riding a beautiful trail like this, why rush it?
As mentioned above, when riding end to end from either direction, you'll have a long gradual downhill for the first several miles and a long gradual uphill for the last several miles -
so you can expect this to affect your speed accordingly, during those portions of the ride. Take a look at the
elevation charts and hills discussion - but here's a preview of the elevation profile:
Try the
Coeur d'Alenes Timeline Tool to see your expected travel time,
and expected arrival times at towns along the way.