Originally Posted by thing
But on the other hand aren't they being retained for a further 12 months?
Not of their own volition so an incentive (reward) no longer applies. They have to stick around for up to 12 months to enable a suitable relief to be recruited/found, trained and assigned with all the knock-on effects (e.g. manning turbulence, unplanned extra work, inconvenience and cost) their premature departure incurs.