With considering long term content, the 7 day payout is definitely not ideal compared to YouTube for example which has ad revenue for all views the entire way. At the same time, I am not sure what kind of simple fix we could apply to allow upvotes on older posts also?
What I have noticed both as a reader and author that when I find a post I love that is older, I often will instead vote the newer posts up by that author. While this makes it confusing in terms of "why did my post about this get so many upvotes while others got less" the system is functioning to reward posts created a long time ago by getting new upvotes today. I often set authors on @steemvoter after finding much older posts I love to reward ongoing creation.
maybe a good way to go would be as @ecoinstant says to turn older posts into a faucet. But don't look at te upvotes anymore, but look at the views in stead.