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Since its spent in-game, some of the tokens can be recycled. Take the example of SIM.

Ideally we never reach the max cap, but still have 'trillions and trillions sold'. If we do reach the max cap, special care will have to be considered as for how to manage it. Every token needs a cap, 2 billion is hopefully arbitrarily large enough for the game to keep playing for a long time.