Chop chop, when older chap was there it wasn’t Link PNG, it was Air Niugini.
To answer your question it was both, some guys there were on 21/21 tours and some on 28/28. And the ‘full time’ guys had the options of POM, CNS and BNE bases. Being based in Oz meant you reported for duty at home base. PX even provided the required firm seats to travel to and from POM.
No paxing in your own time, at your own cost.