Thermostat provides a few ways to help you manage your survey data.
If you are no longer using a survey, you can set a survey as Archived. A survey that is archived can be viewed, and un-archived, but will not accept any new survey responses. Archiving a survey stops any email activity as well.
Survey > Settings > Status. Set the status to archived and click the Save Survey button.
You can permanently delete a survey as well. This deletes all survey settings, responses, emails, and all other data related to that survey.
Survey > Settings > Status. Click the Permanently Delete Survey button to delete the survey, forever.