Thank you. We were supposed to make a prototype, I actually over-did it :-)
Eventually, I'd like to replaced this 'infinite, doomed-to-death' mode with something that actually results in victory of some sorts.
I know what you mean. I made sure to tell my players, "Hey, game is over" at 3 minutes in because that is around the time my content fizzled out, but I let them keep playing a bit longer if they wanted.