I agree that rewarding older posts is one of the stronger points, however for that I and many other Steemians think that the payout should be more than 7 day. At very least 14!
Also adding it's important to add as many possible uses for tips as possible, because I highly doubt one use would motivate anyone to work on this.
I'verecently cleaned up my followers list and unfollowed 300! Steemians for many reasons but most common one was that they were inactive for a very long time. I kept thinking maybe they'll come back, but that seems less and less likely :)