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The bonus will stack with the reward points bonus so you can have both running to maximize your rolls. However the free btc bonus is only guaranteed for the next roll and if after that your requirements fall below the threshold, the bonus will be reduced as well. Just to make things clearer, the picture below shows the maximum your faucet can be boosted to with the current prices.
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Ah, thanks for the clarification. The one-time use bonus is an important detail. Until you said that, I thought it worked on a time window like the reward point bonuses. That changes the math a little for me when determining if I should try to earn it.