Rocky Mountain Cycling Club's High Country 1200k looks very nice. I recall the stretch from Walden towards Granby thru Walden to be especially sublime (before and at sunrise) but the route might go the other way. Loop 1 on Day 2 from Walden to Saratoga to Laramie and back to Walden should also be sweet (low traffic and not too high elevation). Walden to Saratoga is 1300 foot net elevation loss and if you time the wind right, you might not have to pedal. I did the section to Steamboat years ago and if memory serves, also very low traffic. I have camped below the Rabbit ears. Not a huge fan of some parts from Steamboat back towards Granby due to traffic on weekends and inconsistent shoulders but midweek shouldn't be bad. First hundred miles are pretty flat and fast until the left turn of US 287, I recall a store there (control?). Then, a lovely long but not terribly steep climb with potentially favorable winds depending on time of day.
Anyone doing this one?