We left the Phoenix metro area on Tuesday Aug 4th, arriving Keystone SD on Friday night, staying 6 days, then driving 3 days back to Phoenix. It was a blast!
We tried a hybrid approach to the trip there and back. 2 bikes were trailered to SD (except for a 4 hour ride in CO) and 2 bikes rode the entire route. As you might assume, the trailered bike riders were much more rested than the others. It also worked out well for the bike riders as they had an option to rest and re-hydrate and let someone else ride their bike to not lose time. Other than some really nice riding in western Colorado, most of the trip to Sturgis and back is hot and flat.
The riding in South Dakota is AWESOME! Highway SD-16A is my favorite, with the pigtails leading to tunnels with Mount Rushmore framed in the opening.