Is there a time limit that Posts and Messages stay active on the New Feed or do

At this point there are is no configurable limit to the amount of events and posts in the News tab - you can still search for first posts on this site.
As for expiration, there is no such capability at this point but I know this is a frequent request. Please make sure to open an enhancement request with Support.

Hi Mike

Thank you for coming back to me. I will be happy to open an Enhancement Request, can you point me in the direction of how to do so.

Many THanks

The same way you open technical support cases, with Low priority. Support will mark the enhancement and provide you with an internal ticket number that you can then track in the future release notes.