Hi RX123,
which version of galaxy are you using.... for extending backups, it's better to use "extended retention" rules, else, all backups will be retained longer...causes more backup media!!...
Changing retention on Storage Policies, something to be aware of....with the next Pruning or Data Aging, the SQl DB will throw away the pointers to the backups.
Still, backups are still recoverable with the DR tool, if the media has'nt been overwritten yet.
cheers,
Backupster