Usually it is best to keep the Catalog the same time you keep your Integration-Backups. Without it you cannot restore anything. Guess that is why it was done this way.
If you set Data Protection to 7 Days the Catalog will be there also 7 Days and that is good.
if you really want to modify this behaviour you may want to try adding " -keepcatalog {weeks n | days n | until Date}" to the end of your Barlist. Can be used as Parameter for a manually executed omnib-Command as well.