I ran out of asteroids :(
Since running out of asteroids are an inevitability (and mining them only makes the world a worse place), the only way you can progress this game indefinitely is by using the money gained from investors. The investors are pretty happy throwing money at you, even if you're doing absolutely nothing, so long as you give them at least 50% shares. At this point, you might as well rename the game to "Investors Inc."
Also, I managed to accrue 90% tax rate from deliberately not bribing politicians.
I guess the message of this game is that the only winning move is not to play.... Pretty unconventional mechanics for idle games.