A sequel can reveal how much an ending depended on nobody asking what happened afterward.

An ending works partly because the questions stop there. Continue the story and the neat conclusion has to survive contact with ordinary consequence, which it often cannot, and the sequel reveals how much the original relied on the curtain falling at exactly the right moment.

This is worth carrying into your own conclusions. When something is resolved, notice whether it is genuinely settled or merely stopped at a flattering point. Ask what next year looks like under the resolution you just reached. That question is uncomfortable and it saves a lot of trouble, particularly with agreements that feel finished mostly because everyone is tired.