The payout doesn't go to the author anymore, it is returned to the pool now since HF19 or 20. But it moves down gradually like I said, at 5 minutes you get your max potential curation rewards (no penalty), but sometimes it might be worth to vote at 4.5mins or earlier if you think someone else will vote before 5mins too.
If your vote are too small, i.e. they won't even get you a potential CR of 0.001 then that is lost as that is the threshold, so for small accounts it's better to vote a safe 100% vote on posts you think will do well then spread them out too thin.
Thanks for helping me understand this better.