Allow people to switch to another support bubble if there has been no contact or symptoms for 14 days since the last time they had close physical contact. At the moment there is no expiration which means, for example if you move home, by law, you cannot form another support bubble in your new area.
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The rules for support bubbles are clear and understood. The idea is clearly flawed if people frequently switch members or households. However if a single person paired with another household forms a support bubble but has no contact with that person for a minimum of 14 days I think it should expire.