I think this is not a good way to go about things.

The *duration* of archivelogs is less important than making sure they are backed up. So I would be setting an archivelog deletion policy to something like:

RMAN> configure archivelog deletion policy to backed up 2 times to disk;

Then when you issue "delete archivelog all", it will only delete those archives that have been backed up at least 2 times.

If you *really* want to use days, you can use RMAN to do:

RMAN> delete archivelog until time 'sysdate-5';