Without the 7 day limit things would not work well. It would reduce the pool of cash for each payout set as older posts would keep taking from it.

7 days is also not the full story. Unless your post gains traction very quickly then it just falls off the radar far quicker and gets lost in the noise.

If anything I would like to see something that worked against the constant flow of meme crap that in effect hides quality articles. That would be the best thing that could happen imho