Should be no problem.
If you still have those tapes, and ever want to restore something from them, you would need to inventory and them catalog them before you could restore.
If you want to keep the tapes protected, but cut down on the size of your catalog. you could set the TRUNCATE CATALOGS option to 90 or 180 or ?? days. This would leave the header in the catalog, and prevent the tapes from being reused if they are still within the OPP, but all detail info would be deleted.
You would again need to inventory and catalog before you could restore from them