I know when I did my cross country fully loaded with gear, we averaged right around 70 miles a day and that was with 30 plus lbs. of gear per person. The OP clearly enjoys long days in the saddle but it takes a certain mind set to ride 100 miles a day for 30 or so days. If I do another cross country (and I hope I do), I plan on doing it in a more leisurely fashion. I can understand the OP's motivation, however, to do a focused ride like this though.