Dfc I think you have missed the point...the controllers did not CHOOSE to close shannon tower -there was no second controller for the tower because there was nobody rostered and the management themselves would not allow it to operate without a second controller.... not the controllers problem. The controllers may have chosen not to engage in overtime but they did not purposely close the tower.
Maybe later on the staffing of shannon tower will change but at this moment in time that is the rule set by the IAA and not the controller.
Its kind of like saying you only need one pilot in the cockpit because the airspace is quiet......What happens if he needs a break to go to the toilet or gets sick???