To be able to control the alerts generated, you can use the trouble
strategy in the threshold profile, wherein you can choose to be
alerted after a defined number of polls or after a specified duration
as shown below:
If you want to further control the alert generation, you can edit
your Notification profile and set the 'Downtime Notification
Delay' to alert you after three or more continuous failures.
We believe that this will reduce the number of alerts triggered and
you will not be facing the need to delete large number of outages.
Hope this helps.