To help prevent over surveying, the Simple Survey package includes two fields: Survey Sent and Survey Last Requested on. The purpose of these fields is to mark contacts with the date they were sent their last survey. These fields can be used in local automation that sends out surveys after a case is closed.
In the automation you configure, once a case is closed, if that case contact has not been sent an email within the allotted time, a survey email will be sent and the Survey Sent field will be populated with the sent date, otherwise, no action is taken.
This example workflow rule below is set up to check if a survey has been sent in the last 7 days, but this can be altered to any timeframe that fits your business needs.
To edit this workflow rule go to Setup > Create > Workflow & Approvals > Workflow Rules.