I took my first Sammy to Moab from SoCal for a weeklong trip. I'm not sure I'd really call it an "Expedition" though, since some of the time I stayed in motels along the way. The first day and night I, along with the club I was with, drove straight through from L.A. to Moab. We stayed for about four days, and on the return trip a buddy and I took three days to get back.
I did a four day trip to the Dusy/Ershim trail, and another to the Rubicon, and the Sammy worked great for that. I lived out of the Sammy for those trips, and I know I could live out of it for longer than that, but I don't really think I'd want to.
The biggest issue with the Sammy is taking it on the highway. It's fantastic on tight trails, but for driving 1200 miles on the interstate, it isn't the greatest. When I drove mine across Utah, there were places I couldn't even go 55 mph due to the grade and a fairly strong headwind. When I've done that same drive in my '05 Colorado, it's been much more pleasant.