I hit the contemporary era in an endless speed game at around turn 300, the scaling on the money stars started at requiring around 2.13 million money earned and I was above that already I think. The tracker bar on the left was filling up and flashing gold then disappearing over and over until I ended the turn, next turn it said I was at like -2 million money earned out of the required 2.13 million money needed for the star. I'm earning enough that getting another 4 million is going to be pretty easy, but I'm sure I'm just going to go over the integer limit again while trying and get rolled back over into the negatives, so I'm pretty much locked out of those stars. This really needs a larger number storage, I'm closing in on earning 100k money per turn half way through the game with only 5 cities with 3-4 regions each. I'm not even sure 2 billion would be enough for he purposes of tracking money earned over the entire game.