KISS it, straight with indefinite and 24h cycle :):) That way it's simple for everyone and since 24h might be considered universally acceptable nobody considers it a downside as with the other timeframes.
It's true that I sometimes run into articles that are very valuable and were written a few months ago. We have writers around posting their stories. They can't be denied an effort reward after 30 days I think.
Long term rewards can be done via tips. Any individual vote has almost no ability to pay someone unless it works with many other users. This means that with the exception of a few whales, the long-term payouts would only apply to content that goes viral on steemit after more than a week delay. Possible, but unlikely.
We need tipping on steemit!
https://steemit.com/steem/@snowflake/let-s-get-tipping-going-on-steemit
There are GitHub issues for it :)
https://github.com/steemit/steemit.com/issues/401 https://github.com/steemit/steem/issues/690
This is a good approach. I think the calls for long term payouts would greatly subside with an effective tipping system.
A blockchain feature that makes sense for tipping is a change purse (with a user-defined max balance) that can be used to receive and send tips with only the posting key. Or alternately some sort of rate-limited tipping ability from the regular balance with posting key.
Perhaps with an automated aspect: if the payout is already made, you can assign a certain amount to be tipped by your simple upvote.
Then after the one week payment, let unlimited 30days payout cycles active...After mass adoption it would be very likely some gem-posts to attract several votes in couple of 30 days periods... Even not many votes would add up the rewards after months, years of the post existent.... After all the posts will be on the blockchain for eternity...
PS I guess it is vulnerable to abuse the reward pool, right?