There is not a way to change the timing of the news items in the stream. This is based on the user reading items in the stream by clicking through either in the browser or mobile and the priority for the news streams. There have been updates to the feature in the cloud (not that this helps you right now) but nothing that allows someone to configure timing or directly influence the algorithm). You would not be able to use the API to change the behavior of News.
Having said that, it would be possible to create a new tile that presents news items to the right of the news stream in Jive 8 and control how long those items stayed in the tile view. You would then remove those from the News streams. The downside is that this doesn't push notifications to users and doesn't flow into mobile via the News stream.
thanks for that - bit of a shame to choose an arbitrary time for drop off that isn't changeable, but good to know.
I have submitted an idea to Jive, regarding being able to suppress certain news stories from the news feed.
We have a lot of outdated content on Mondays and this would improve our home page drastically.