Then there's the 7 day payout period that makes it really hard to put in the effort to create evergreen content, because the evergreen level rewards aren't there

I really agree with this. Evergreen content is not only useful in 7 days. Someone might find it a month later or a year later and it's still relevant.
However, the author will only get the reward in the first 7 days.

It's true, someone can give tips to the author whether in the form of liquid hive or other tokens. But of course it would be easier if readers could directly give a simpler upvote.