When your Harvard ID expires, you won't be able to access your AGOL account anymore, but your content will remain. You can do the following:

1. Transfer ownership of your content to your Harvard teammates before your Harvard ID expires (recommended, you can do it any time)
2. Ask CGA staff to change content ownership for you after your Harvard ID expired (fill out the form on https://gis.harvard.edu/contactus)
3. If you need to transfer ownership of your content to another user from another AGOL organization, you will need to work with the new owner to do the transfer. See https://community.esri.com/t5/arcgis-storymaps-questions/can-you-transfer-a-story-to-another-esri-account/td-p/557639. Use the ArcGIS Online Assistant, login to your account, select the content to be transferred, pick "Copy Items", then login to the new owner account to complete the copy.
4. You may also wait until when you settle in your new organization and activate your new AGOL account there, then ask CGA staff to change content ownership to your new account outside of Harvard (fill out the same form as above). This assumes that your new organization also has an organizational account of AGOL. Personal free AGOL accounts can't received contents from organizational AGOL accounts.
5. Abandon the content to let CGA staff purge them after a few years.