I love spreadsheets and build all sorts of massive spreadsheets to model scenarios, but ultimately I know only one truth, and that is that my detailed assumptions will be wrong.
I have no idea what future inflation, share market return, real estate returns , interest rates, economic growth etc will be. I couldn't forecast next year with any certainty, much less 40 years+.
So for me, despite all my spreadsheeting, i am attracted to simplified goals like save 25x what you need to spend. And then maybe add a bit more to address the fact that I might not be able to be perfectly efficient in my money management, and to err on the side of caution a tad since I have many years to finance.
I have tested this simple assumption against my detailed spreadsheets, and I don't have any way to say one will be more accurate than the other. In the end it's easier to explain to my wife that I want us to target a simple NW target before we fire, The mix of investment vehicles we hold today is not so important, as it will evolve with time.
We prob do have too high a percentage in super (about 40%), and towards the end of the 15 years before I can access super, there is a risk we will have to draw against our home. Again, a lot can happen in 15 years so I am not particularly nervous about this issue. I suspect we may do some part time work to mitigate this risk.