FB, understand your reluctance to spill the beans yet. But If you were in SoCal, and were planning on riding to the Un, how many days would you allot? And what mix of slab versus "interesting" roads would you be driving?
I have several scheduling constraints...
Well, I actually DO live in SoCal. Last year I went to Wisconsin and allowed 3 days each way. I got to sightseeing a bit in Yellowstone, and it took me 3.5 to get there. But a lot of that time was spent traveling north. So, since this next UnRally won't be that far to the north, I still figure 3 days as a minimum, if you figure 700-800-mile days (rough estimate and assuming you get yourself to Vegas on the afternoon/evening before your official departure day). But I also tend to start my riding days at 3AM and be done riding by 5PM, rack up about 1000 miles on the first day, then just a 500-600-mile cruise on the other two, and so forth. So that can skew things.
There are interesting places to visit in all states. But I think you're wondering about interesting roads. That's an entirely different kind of trip. If you've got scheduling conflicts, go through the middle of the U.S. and once you're past Denver's approximate longitude, just hunker down, make miles, and leave the scenery for some other trip when you have the time.
The Un Rally is always scheduled on a Tue-Thu which gives attendees 3 days on each side for travel. For a cross-country schlep like you're talking about, you're going to need all of those days, and maybe one or two more depending on weather, traffic (wrong time of the day through Denver or Chi, or ??? can add hours) and construction (the general rule is stay to the south and get good info on the internet regarding delays). And don't forget a day or two minimum for recovery upon your return (at least that's a requirement for me now that I'm in my 60's).
In other words, my trip may not be your trip. But that'll give you an idea of what the minimums would be, if you're not a 1000-mile per day Iron Butt Rider, in which case all bets are off.