I do manual curation and my method is not very sofisticated:
I read, I like, I vote, I follow )
It doesn't work very well in August, slightly better in September and in October I've found myself among trending most effective curators)
So, one thing is that average quality of curation is (from my point of view) improving, new good authors are mostly discovered really soon, I believe thanks to curation guilds.
Another thing is that economical intensity to look for new authors is always there, because some of mine preferred authors now just a few minutes after publication already get a few dollars from voting bots,and that would mean no curation reward left for me, this making me rather to safe my vote for someone with 0.1$ only.