My experience has been that the benefit of a rest stop begins to diminish after 20~25 minutes, unless you’re stopping for a good sit-down meal, or sleep. After 20 minutes I find that it gets hard to get rolling again.
I’d be more likely to take those one hour breaks and distribute them into 3 twenty-minute breaks, to make the 4.5 hour runs more humane.
My buddies and I rode Pgh-DC in three days in 2004, stayed in motels, no support vehicle. (trip report here) The daily breakdown was Pgh-Meyersale (102 miles), to Williamsport (115 miles), to DC (104 miles).
Pgh-DC in three days is one of the stooopidest things I’ve ever done, and I’m the guy who planned the trip. Ugh. (This was before the Savage Tunnel and associated trails were open).
There are Ultra-athletes who semi-annually ride Cumberland-DC unsupported non-stop, and the normal best time is around 18 hours. Check the C&O Yahoo Group.
GAP has a speed limit 15 mph. In addition, first 10-15 miles counting from Boston has numerous road crossings (IMMSMC at some point every quarter of a mile) making average 18 mph pretty hard 22-23 mph between stops.
I have done this in relay form, it’s pretty fun, we got permits from the C&O folks, did it 3 years in a row. Definitely start on the C&O at daybreak and spend the overnight on the GAP, trying to do the C&O at night is a bad idea.
This would be a super challenge for one person, when we had alternating relay teams we still barely managed to squeak through, finishing within 20 minutes of 24 hours every time we did it. Maintaining a speed of greater than 18 mph on the trail is really challenging over long distances.