Catalog files for BE 2010 only get removed when either truncate is enabled or when the media they relate to are overwritten/erased. I am not 100% sure what the effect is on the catalog files if you retire and then delete the media within Backup Exec as to whether this would also remove the catalogs.
If you just stop using the media (tapes or disk files) OR delete the media without Backup Exec being aware of the deletion then the catalog files will remain.
The truncate catalog files option will remove the older .FH files (although in earlier versions of BE changing the truncate setting after the catalog files were created would have no effect on existing catalog files and I am not sure which version we enhanced BE so that the truncate applied to all files and not just those created since enabling/changing the setting)