I'm looking for long, high, roadless (and ATV-less) trails, greater than 50 miles. On the Colorado Trail and the CDT in Colorado, 25 miles is about it, and often much less. The PCT through parts of California is probably the best example of what I am looking for.
I don't mind an occasional road or two, but it is amazing how difficult it is to find trails that aren't crossed by highways, gravel county roads, or shredded MC/ATV tracks. From what I've seen, "on the ground" info is the only info that can do the job. Trail guides often ignore the occasional, but well used ATV track or ranch road. So, unless you've "been there done that", hold off.
Here are three examples:
The PCT from Kennedy Meadows to Tuolumne Meadows
The Wind Rivers from Green River Lakes to Sweetwater
The Grand Canyon's Beamer, Escalante, Tonto route isn't high, but IMHO is very worthwhile.
What other sections can you suggest? (And a little cross county to force a connection is OK.)