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Very tricky indeed @ironshield! Generally you may say that the better the post does, the earlier the optimal upvoting moment comes. From my experience 25- 29 minutes is optimal for very low (<$2) earning posts. But for posts that go sky high the best moment may be much earlier, even around 5 minutes. Its a trade-off between increased Weight and the share of the vote going to Curation.

Please share your findings regarding the Curator Gem if you have any, as I am in the process of gathering data!