Mmmmm....lets have a closer look at what you claim.
It isn't 8 years to command.
Right now it is a little above that - and that is without the incoming influence of a change from retirement age 55 to RA65. A 10 year stay of execution for the seniors is going to do wonders for upgrade times.

Plenty of discussion and number crunching on the Fragrant Harbour site about the actual impact. The consensus seems to be command in the 13-14 year time frame IF expansion keeps it's current pace. So, 8 years is a complete furphy. If you work in HK you would know that, or you are being disingenuous.
Secondly, you have to compare apples to apples. If you want to talk about time to command, are you talking about in Australia? If someone takes a DEFO spot in Oz, are they prepared to move to HK to take the command (in 13 years)? That would entail commuting or dragging their family up, which introduces a raft of considerations that don't have to be contemplated if you are going to stay in Oz. Pollution (unbelieveable and getting worse), schooling (good luck in getting your primary school/high school aged kids in anywhere decent) etc. Because there will be no command slots in Australia. So...if you are not prepared to eventually move in XX years when you are probably very settled in your Oz life, when can you expect to get a Oz command? Given the limited slots, RA65 to reduce turnover and many, many, many people ahead in seniority who will be bidding for slots I think a newbie now would be very lucky to ever see one.
Lets keep comparing. Yes, the pay goes up at the four year point, so you are now overhauling a
VB pilot who joined the same day (which is only fair if you fly something bigger and had higher entry requirements to begin with). And the pay will incrementally increase as well. But - what's the upgrade time in
VB? Right now I believe it is around 5 years? So, the DEFO just overtook his
VB mate in the $ stakes, then a year later his mate gets his command (caveat - assuming B737) and leaves his DEFO mate in the dust again.
Food for thought. Not trying to tell people how to make their decisions, but wish to add some clarity and actual considerations to the mix.