Of course one needs to assess the relative risks of your different options, and no one said that investing is risk-free. However, I must disagree with this premise.

What exactly is the "much higher" risk of having vs not having a mortgage? There shouldn't be any management overhead; put it on autopay and you don't need to think about it. I'm guessing you mean the risk of default in the event you find yourself unable to make the monthly payments, and consequentially losing your house.

Sure, the type of person who thinks solely in terms of monthly payments and wins a big chunk of change in the lotto would be well-advised to pay off their mortgage because (speaking in generalizations) they aren't making great financial decisions in the first place.

If you manage your finances prudently, I don't see simply having a mortgage as a major factor when comparing the risks of investing excess cash vs paying down the mortgage.

In a nightmare scenario, where you've invested all your excess cash and then find yourself unable to make mortgage payments in a down market, you still have the investments to draw on. Sure, you may be rather unhappy about taking a 20% haircut every month to make your mortgage payment, but you won't lose your house.

Plus, you'd still have other options in this scenario. Maybe you can negotiate temporarily reduced or interest-only payments. After all, your bank would probably prefer to not risk losing a sizeable chunk of their principal in a foreclosure. In a more systemic crash, maybe there's government assistance, deferment, or the like available (eg see 2008's https://en.wikipedia.org/wiki/Housing_and_Economic_Recovery_...).

And just because one doesn't have a mortgage doesn't make you immune to the risk of losing your home. You're still on the hook for property tax payments, and failing to manage those will end the same way.

Of course, this all assumes you're otherwise making good financial decisions anyway. Your mortgage should be affordable when you're making 100% of your normal and expected salary, and that you haven't bought too much house because you suddenly find yourself making 200%.

We should also understand that not everyone approaches personal finance the same way. I simply don't view a mortgage as some kind of existential stressor, and cannot relate to the "emotional burden" you allude to. It's just one other line item in the budget.

On the other hand, my other half hates even thinking about finances, and would certainly get anxious thinking about and trying to manage this kind of stuff — that's why I deal with it :)

For someone like that, I can understand how eliminating a mortgage can have value to them, for the reasons you describe. However, we must admit that this isn't exactly a rational thing, and it's not doing anyone any favors to pretend otherwise.

Let's run some basic numbers:

With a $1m loan at 4% APR over 30 years, you will end up paying $719k in interest.

This $1m loan will have a monthly payment of $4,774. Let's say you were to double your monthly mortgage payment, and pay $9.5k every month. This would get you paid off in ~11 years, and reduce your total interest paid to $232k, a 'return' of $487k over a decade.

On the other hand, if you paid your mortgage for 30 years and you invested your extra $4,774 (assuming VTI's average historical return of 9.81%), you'd end up with $10.5m, a return of $8.8m over 30 years.

Now contrast with paying off your mortgage in 11 years and then investing $9.5k every month for the following 19 years. You'll end up with $6.4m, a return of $4.2m.

$487k in interest savings + $4.2m of investment returns = $4.7m total return

Is paying your mortgage off early really worth $4,100,000 to you?