I left it running over night, which got me up to about 750 generations. I watched for a few generations then went to eat breakfast. When I came back, it appears generation 822 "won" the game, so I watched the replay.
At about 220 meters, the floor generation stopped but the car kept going, falling rather.
At a height of -2920 meters it stopped altogether.
I've watched about 250 generations, and it seems that luck has as much as anything to do with the performance of any given car. Sometimes a car will make it farther than it's elite clone will the very next generation. In fact, clones seem to get stuck rather often, allowing possibly inferior cars to finish well beyond them. When this happens, whatever "good genes" that clone had are lost, and it often takes many generations for a car to again take the top spot.