Again, correct me if I'm wrong, but you do not receive curation rewards for upvoting posts that are less than 15 min old, and you receive twice the curation rewards for upvoting posts that are older than 30 minutes.

I'm pretty sure this is incorrect, because votes in the first 30 minutes are shared with the author, which in this case would be yourself!

For reference:

dan: There is a linear split between 0 and 100% as time from post goes from 0 to 30 min. If you vote after 5 minutes then you only get 16% of curation reward, the rest goes to the author.

Link: Voting between 0 and 30 minutes

rainman60: You have to remember this "penalty" to curation rewards is actually a bonus for the post author. The earlier you vote for a post, the more of your rewards go to the author of the post instead of you. So by voting early you are saying "This was a really good post, the author deservers most of my curation reward"...

Link: New Curation Reward Algorithm: Penalty to Early Voters