When would I want to expire a survey vs. deactivating, or visa versa?
Expiring a survey allows you to close a survey without losing participant or response data. This would be useful if you intend on reopening the survey at a later time. Deactivating a survey closes a survey and wipes out all response and participant data. If you want to keep participant and/or response data, you should export that data before deactivating the survey.