Over the years, I can count in one hand the number of people who have returned to FR for a second bout. I will add that three of the aforementioned left again, obviously having enjoyed the experience so much on the first occasion! All of those were Captains, two decided to go back to the RHS long haul jobs that they had initially left for.
I am aware of one ex-skipper in the ME who would come back, however only if all roads home became exhausted. Remember, there appears to be the increasing likelihood of former FR skippers who have migrated east being hired back west as DECs at Norwegian.
With a new Director of Flight Ops, the policy for returnees may change; especially relating to command ready FOs. It all depends how many bites of the carrot that they get I suppose?