I have had some friends who were interested in joining. I wanted them to join so I sat down with them and tried to explain things as thoroughly as possible. I didn't want them to be in for any unpleasant surprises. I was able to explain just about everything except for that. I had a pretty good answer for how things worked until I got to that 12 hour window. When they asked "why can you only have rewards taken away during the last 12 hours?" I didn't have a logical answer for them. I could only say, "that is the way the system works".