It appears to be a no issue, the tapes expire at their due time, not at 
"volretent".  I was able to confirm it after some testing.

As per EMC:
"...the NetWorker media database reporting via mminfo command can
only report the record as a ssid/clone-id pair, not just for the ssid.
This is why your volretent value is specified on the source volume still
as the longest date."

That is volretent can only report the longest of SSID/CLONEID combo, and 
cloneid happens to be the longest.  However NW expires tapes based on SSID 
provided retention period.  It looks like rather bug or broken logic for 
"mminfo" reporting, because in the case when clone retention is longer then 
source volume, "volretent" value becomes incorrect and in fact does not report 
VOLume RETENTion of this queried volume.

Oh, well.

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