If you make a backup of a VM and then delete the original VM, the retention period will depend on the retention period that you select when using DR to backup.
When using the backup Job wizard, In the Retention Policy page, accept the default retention policy or specify an alternate retention policy.
In this case you are talking about maintaining a VM that you are ready to delete, therefore it is no longer needed, if you want to have a copy Just in case then I would suggest using the yearly backup type. that way you maintain the backup for a year and you have enough time to restore if anyone requests the VM.
Lots of useful info in this guide http://techontip.wordpress.com/2011/07/25/understanding-vmware-data-recovery/
and in the offical manual: http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vmware-data-recovery-administrators-gu...
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