Can you create a segmentation and leave it alone and it will update automatically as users come in and out of that segment, or are the segments static that need to be reapproved ?
They are dynamic -- as long as they match the criteria you set they will update as values change.
a good note from DOCS:
"Segments currently do not support In Past and In Timeframe constraints on filters. That's because segmentations only check for updates when a change data value is logged. These values are not logged for things that change automatically, such as formula fields and dates."
If you're relying on it to update dynamic content in real time, note that there is a delay. e.g. a lead won't be in the new segment for a few seconds
Retrieving data ...