I'm currently on a back to back that has 19 segments (excluding repositioning flights)
$878 CAD: YVR-PHX-JFK-DCA-MIA-PTY-MIA-PHL-DFW-YVR
$960 CAD: YVR-PHX-JFK-BOS-DCA-MIA-PTY-MIA-PHL-DFW-YVR
For the 2nd trip, I'm in PTY for 2 nights and in PHL for 1 night. I could have routed in an extra couple of segments, but I'm actually glad that I didn't because pretty much every flight from JFK-DFW on the first trip and from BOS-PTY on the second trip (I'm currently in PTY so I'm not sure how the rest of the trip is going to go yet) have been delayed.
I only had lie flats from JFK-BOS (still the stupidest use of a 321T ever), but otherwise was on A320s/737s/e75s.