You can configure the following setting for the notification service.
|Item||Use this item to|
|Notifications lifespan (in days)|
Specify the number of days after which the notifications expire (since their creation). All the images that are linked to these notifications will be also removed. If the number of days set to 30. For example, on February 28th, all the notifications and images created before January 28th (excluding the items created on January 28th) will be deleted.