Once you have done a permanent failover your replica became original VM on remote site, so you could perform replication job once again followed by another permanent failover to primary site (to be sure you have latest state of the VM).
However, it’s highly recommended to use Replica mapping
as you have your ex-original machine on primary site (it will reduce amount of data to be transferred back).
Regarding your question: “ie what would normally be accomplished by a "Fail Back"”
Please see detailed process explanation on Replica Failback