The longest trip I've taken so far has been a 1,500 mile round trip (last summer) between SW Ohio and the Upper Peninsula of Michigan. I traveled two days up, two days back, with three days of R & R in between. The longest day was 523.8 miles; the shortest was 179.8. I thought that my fully-loaded 2006 VN 750 handled it beautifully; and I was surprised that I didn't find it more tiring on my mind/body. (You're
talking about a much longer
trip, however ~ including badlands
I have a Plexifairing 3 windshield, which provides excellent coverage from buffeting winds, bugs, cold, precipitation, etc.
All of my luggage held up well. I stuck a magnetic bag on the tank and hooked a tailbag to the passenger seat. I yoked saddlebags under the seat (no saddlebag supports), and bungied a duffle bag to the stock rear rack.
On a long trip, ear plugs REALLY help reduce stress/fatigue. (I use ETY-Plugs with a cord that keeps me from losing them at gas stops.) And a throttle lock is helpful for those long, straight stretches.
Eventually I would like to get a more comfortable seat ~ either putting an Airhawk on my stock seat, or replacing my stock seat with a Corbin. (On this trip I sat on a 1'-square cross-stitched foam cushion, and the stuffed tailbag was a nice lower-back support!) Floorboards might have been nice. (I now have a pair special-made by Knifemaker, but I haven't replaced my footpegs yet.) And I should have gotten large rather than medium saddle bags.
Here are a couple photos of my bike loaded up.