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My answer to the practical part might be that we don't really balance it and instead just lower priority based on historical slop and earnestness ratios.
This may not be like a valve that you can throttle and open up again:
Crowding Out after Incentives Are Removed Incentives for Prosocial Behavior
i.e. if you lower the incentives the motivation can drop and remain permanently lower than it was before any incentives.