Re Darwin
Mods please excuse the thread drift. I can't speak for RAAF but the retention factors would be joint, I suspect. Certainly Army has problems keeping people in Darwin, particularly the CAPTs and SGTs.
With a few exceptions the mates of mine who have endured Robertson or Larrakeyah postings have gone on the record with their career advisors to state variations of the following: "I will not accept another Darwin posting, I'll pull the pin if I'm posted back here in 2 years' time".
About 10 years ago Army had to split 1 Bde to send half the units to RAAF Edinburgh to provide respite postings. There was also a need to provide year-round access to training areas, but that's not related to the Darwin retention problems.
The National Audit Office studied APIN about 15 years ago and came up with a staggering figure of how much MORE it cost the taxpayer per member posted to Darwin.
So lots of reasons not to post valuable people to somewhere most Australians don't want to live.