A client asked me recently why he should back up the SSISDB database. While you can recreate everything inside of the SSISDB, it will take time and you will have to remember exactly how all of your variables were set. Restoring the backup decreases this issue and having a backup allows a server to be redeployed quickly. When you do back up the database, make sure that you remember to backup the database certificate, which is created when the SSISDB is created as well, as you will need this to do a restore. By default. the recovery model of the SSISDB is set to Full. If the packages in SSISDB are changing minute by minute, full would make sense, but given that an SSISDB contains packages which are run on a scheduled basis, most likely the changes made are infrequent. Change the recovery model to simple.
SSISDB is a real database, just like ReportServer, so don’t neglect it just because you didn’t create it.