Historical Node Segment Retention

How are segments retained on historical nodes? I see that certain segments are loaded on the historical nodes, regardless of whether they’re queried or not.

Is there any policy for unloading (but not deleting or removing) segments from historical nodes if they are not used or queried after a certain period of time?

If they are kept around forever (via the loadForever rule), is the expectation that you will have enough storage across your pool of historical nodes to accommodate your entire data set?

Thank you