So are you talking about compoound interest on an alternative investment with greater certainty (fixed bank deposit)?

Hmmm. So if I made a modest 6 percent per year on my 20k, I can expect to have 200,000 in 40 years (without added additions). That doesn't seem to match what a want, but then again that assumes I have zero net addition which I reckon is unlikely.

I get approx. 5000AUD a year from Centrelink, and don't really spend it so lowers it to 17 years till house. This is an oversimplification since I donate to charity and will probably have a job that makes more money with a lifestyle that costs money but this gives me an upper bound. If instead I can add 10,000AUD per year to my investment I can get to 200k in 10 years which seems like an attractive prospect

the principle barrier to this is that now i have my money tied up in illiquid assets that are longterm in their strategy. If I liquididate now I could be seriously damaging future gains no. Maybe it's best to wait for those stocks to appreciate then to sell them and place in an index fund (but a fixed deposit account is safer yeah?)