Retrigger delay for an alert specifies the minimum delay (in days) between subsequent retriggering of this alert after its initial triggering. An alert will only retrigger if the previous alert has been closed and if the account still meets the alert conditions.
For example, if the retrigger delay is set to be 7 days, the alert will retrigger for an account until 7 days after its first triggering once the previous alert is closed and the account is still matching the criteria defined in the alert rule. If the alert is closed after 7 days since its last triggering and the account still matches the criteria, the alert will retrigger any time after it is closed.
It can be a useful feature to leverage for your specific use cases. For example, if you'd like to be reminded of a certain situation more frequently, e.g. usage decline, overdue payment or no interaction, you might want to set a shorter retrigger delay so that even if you close an alert for an account after dealing with it, you'll still be notified that certain situation has not been resolved with that account after the retrigger delay has passed.
In other cases, for example, if you have a renewal alert to remind you of upcoming renewals in the next 60 days, you might be able to resolve the renewal situation with an account sooner than 60 days and the account still meets the conditions defined in the rule - having a renewal date in the next 60 days; you might want to set the retrigger delay to be at least 60 days so that you won't get the same renewal alert if you close the renewal case with an account sooner than its next renewal date.