I did about 780 miles on two 750,s in 26 hrs. Each time.... Since 07
Both times were first highway rides of the year, actually more than a year. One was a strutted rigid.. The other a just got running yard find. My buddy had put about 50 miles on that then I rode it about 15 miles, sat nite worked on it Sunday, then hit the road Sunday around 6 from Calgary Alberta.. Was in Shoshone Idaho, by dark next night.
Its largely mental, and ignoring minor pain, and finding your riding groove..the rigid, after 45 -50 minutes, I step off for 3_5 minutes...and get right back on. It works for me.. But you have to have clearly defined goals, and be able to sleep anywhere,
and at odd times..
If I am broken in after a few long rides, its a bit easier.. I have gone LA to here, and Sturgis to here, in 30 hours.. Its around 1150 miles.. The La one was on a touring twin. Never used a windshield, although one bike had a fairing with shield missing.
Just do it..adventure awaits you..