Searching did not turn up anything on this topic. Perhaps I am a poor searcher.
We've been wondering what to expect as we exhaust our battery capacity. Today, I found out.
We had been estimating range by adding miles traveled to the silly miles remaining on the dash display. Typically the sum of those two numbers would be around 90 miles at the end of a 70-80 mile trip. Today, I decided to run it on down. We hit "---" for the remaining miles for the first time. I noticed 4 miles and the next time I noticed, it was "---". Onward, Through the Fog says I. I got home several miles after it went below zero with about 100 miles on the trip and went out driving up and down the road to see what would happen. At about 106 miles, it went into "turtle" mode. I immediately turned around and headed for home, less than 1 mile. About 200 yards short of my charging connection, it stopped moving entirely. It shifted itself to N and refused to shift to D or Eco. All electronics continued to work. I walked to the building where I charge, got a golf cart and towed the Leaf in with the golf cart.
1) at modest speeds, you have at least 10 miles left when your "miles to go" goes below zero
2) once you hit "turtle" mode, you likely have less than a mile left