Excellent post Taraz!
Being mostly a poster of "timeless" content I agree with your take so much. Perhaps groups is something that needs to be implemented in steemit, something to help categorize the material and maybe each category has its own payout timeline.
Something else that could be done now is the creation of a community, like @curie, that finds good content that isn't ephemeral and reposts it once the 7 days period ends, again and again if it seems to have traction. And the rewards of the repost would go to the original author. Perhaps they could keep the SP to upvote other good content.
Anyway, just a thought.