Hi Tarmac12,
I found that 1 per semester was enough if working full time. There are some half units and I tried 1.5 a couple of times but this ramps the workload right up and can reduce the quality of your work.
There was a story of someone completing the whole masters program in 18 months full time - not sure if true. I would allow 4 years if you have a job.
Can't recommend the UNSW course highly enough and it certainly accelerated my Airline management career. I found the benefits came even before the qualifiation was obtained as the assigments facilitated interaction leading to opportunities.
Good luck.