Same as TomP45, my game progress slowed down dramatically when i hit 24 billion angel investors. I can make everything on right side screen to 500, and oil company at 662, but invest more into oil compnay brings very little return at this point. And the daily angel investors gain are not growing much, even after serveral resets.
Right now, in testing, I have an account at 750 billion Angel Investors, and I can get up to 500 of everything within an hour-ish of play. There's lots more upgrades and achievements coming soon though!
 "AdVenture Capitalist"){kind=icon}
 "Papa Louie 2: When Burgers Attack!"){kind=icon}
You're exactly right!