Since Steem is all about rewarding content producers and curators, I think it would be helpful to continue to support high quality content after 7 days, including curators. Right now curation rewards drop off to near nothing after the first 10 upvotes. Why not use a kind of recency power law to reward big upvotes for older content? If Steem held content that continued to pay and a new curator could benefit by promoting that content, I could see investors buying into the platform. Paying for votes to get a post on trending is one mechanism encourage investment, as is delegating SP to bid bots. However, as long as Steem only rewards content for the first 7 days, it encourages low quality content and devalues all of the old content, since that content is all available for free. Why buy the cow if you can get the milk for free?