Yep, don't power down. Also, keeping the 50/50 split for rewards is a good way to keep your wallet flexible. You have some SP to power up, and you have SBD and Steem that you can exchange, if you really need to. This way there's less need to power down.

On the topic of rewarding content beyond 7 days, there's the tipping service, if you really want to reward someone.

Finally, given the way Steemit incentivizes content (and how there's no easy way to navigate the blog), maybe it's just time we accept that the platform is not the place for evergreen content. And that's not exactly a bad thing. Otherwise, like you mentioned in this post, there are ways around the 7-day rule to help really good posts continue earning and make sure they don't get buried under more recent content.