As far as Avg speed, the ride usually starts around 7-8am depending on which start venue you begin from, and I think they close the course and start bringing you via a van at around 5:30 or 6pm. So you conceivably have 10-11ish hours to get it done on the first day. The 2nd day starts around 7am and the last rider usually comes through around 3:30 or 4pm. So you have another 8-9 hours on day 2 to make it 68 miles or so.