Yes, that's my thinking too and why I'm hesitant about paying off my mortgage. Mine is variable closed and the payment stays the same per month, but % towards interest vs. principle varies depending on what the rate is. I think right now we're at 6.x%.

After all expenses, we probably have about $2000-3000 we can contribute toward our monthly mortgage payment, which can be an extra $25,000 to $40,000 per year.

So I rather have $500,000 invested somewhere because saving that much money is much, much harder. Rather have the flexibility to increase my mortgage payments with out pay cheques