For things that are paid out, I have this:
https://helpienaut.github.io/steem/curation_analysis.html?account=michealb&votedUser=
which you can use as a guide. It sees the affect of if you changed your vote timing (while preserving the vote value).

But yeah, it definitely depends, something you know is popular, you have to weight the early penalty loss against what you think you'll gain from being early.