You're right on target. I figured this out a long time ago. We're basically told that in order to get better curation rewards you should vote on posts that are going to go big.

People are voting on posts that are already big from which the posters themselves are getting all of the curation rewards though.

The best thing to do is to find someone that only has a few votes that you think is going to go big and vote on them after 30 minutes.