I'm afraid it doesn't work exactly as expected, or as it was designed.
I was already wondering why my recent trips didn't generate that many points.
Yesterday I drove almost 90 minutes (appr. 175 kms) and when I stopped for a coffee after 165 kms because I was a little early, I got back in the car and my phone had hung at exactly the position I was in at that moment. So, Waze knew until I stopped for the coffee where I was. I took out the battery, rebooted the phone and started Waze again and drove the last 10kms.
However if I look in my archive (http://world.waze.com/WAS/gpx?id=1103048
) and more specifically the first route on that day (rm_07_04_10_2800527577_37478.gpx), only the final part of this trip was recorded. The trip back home again didn't even show in the archive at all.
that you have to have a live connection all the way up until you have properly shut down Waze. Any loss in connection or any crash/hang of the phone until then makes you lose your trip.