Why does the scenario stop producing airmail stamps with at 30 minutes left in the last round. If you don't get lucky with lost mail, you just wasted 3 hours. If you do not beat the queen, you do not get any rewards because even bronze requires you to beat all three rounds. I have tried cramming as much mail as I can down my people's throats but it still stops making stamps. I have tried starving them of mail and not delivering more until airmail has reached 0 and it still stops making stamps. I have razed my cities so there is no living human being on my islands and rebuilt them but it still stops making stamps. I did 3 runs of the scenario and this didn't happen. The last 3 tries, it has happened 100% of the time. On one of those three, I just got lucky with lost mail and got just enough stamps as rewards to win. If this is intended, why have that last 30 minutes? Wouldn't it be better to just waste 2 1/2 hours instead of 3?
EDIT: Don't get me wrong. I love the challenge. It would just be nice to not have it cheat me out of 30 minutes of the scenario.