3rd for the JD and GR, we did both this year - they were great. I too started overnighting on the Smith - Ran it all but one year from 1999 to 2011, 4 2 trip years and one back-to-back; took off drove back to the put in to meet another trip and put in the next morning.
Other rivers to consider NF and SF flathead (SF is pack in and $$ but well worth it). SF Snake there is an overnighter that can be stretched to three We put in higher, camped at the first campground on the stretch and then the last, and rowed out on the third day... There are other rivers where you may need to get creative but lots of people float multiple nights on the Yellowstone by either staying on publicly owned islands or at fishing access sites. You could probably string trips together like that just about anywhere.
I'd like to find more trips too, I rarely do the Smith anymore thanks to their dog policy so I'm always looking for more overnighters... Bring them on!
Yesterday's gone on down the river and you can't get it back. - Agustus McCrae