Well if he averaged 60-65 miles a day, he could easily do that in 7 hours even with the heavy load he carried, so no real reason to think he had to have ridden at night, especially since it sounds like he got up with the sun. Even taking into account food and his library stops, get up with the sun, ride 2-3 hours, piddle around some, ride a couple hours, piddle around some more, ride a couple hours, and you're done travelling well before dark.

That's a lot of miles, but he took over 2 months to cover it. Sounds kind of leisurely almost. As far as routes goes, I think that's why he covered so many miles, to find those useable routes.