I recently did the shuttle and float from Ruby Ranch to Mineral Bottom. The shuttle took about 2 hours each way.
There's about 14 miles of winding dirt road from I-70 to Ruby, and a steep, winding dirt road to mineral Bottom, both of which slow one down considerably compared to the pavement.
To answer the original question, the float took us 3.5 days on the river (rafts) but we had to motor a total of about 4 hours, so it would have taken at least another full day. (This was an early October trip at I believe about 900 cfs.)
On a side note, my buddy and I did the drop off at mile 70 (Bowknot Bend) and hiked over to the other side where we met the boats again after they did the 7 river miles. The hike over is an hour tops but the rafts took about 3 hours (they got stuck a couple times in the shallows...). Photo looking east from the top.