The 30 minutes was pre-HF20. The one-hour wait idea was probably based on a misunderstanding.

I've read from many sources that, post HF20, 15 minutes is indeed the time after which curators get to keep all their curation rewards. But if your goal is to maximize your curation rewards, it's not that simple. There is a reverse auction in which those who upvote first get a larger share of the curation rewards than those who upvote later. Front-running whales is obviously the most profitable way to curate even if you do it before 15 minutes and lost a portion of the curation rewards back to the pool. From what I've been told, only the author loses all curation rewards by upvoting their own post before the 15 minute mark. Because authors generally no longer upvote their own posts before the 15 minute mark, a larger share of the curation rewards go to other users. This should favour small accounts.