As it happens, there is one of their aircraft there every week for 4 or 5 days. I see it come in from Nauru on a Sunday evening and it leaves again late Thursday night or early on Friday - it is part of their scheduling (although possibly it doesn't represent good utilisation).
Seeing an a/c there for a week is not unusual. They appear to rotate different aircraft through as the registration of the one that leaves is usually different to the one that returns a few days later.