. . . The most important consideration, though, is the interest rate on the mortgage. If it is above the after-tax return on secure investments such as a Treasury Note of equivalent maturity, it is best for most people to pay it off.
The converse of that is certainly true. . . If secure investments of equivalent maturity offer better after-tax return than the interest rate on the mortgage, it would be foolish to pay off the mortgage.
But this statement assumes much about the problem that is not neccesarily true. Run the numbers and see for your situation. Or don't run the numbers and decide based on your emotion, if that suits you better.
Example: (Case 1)
Investor has:
paid off home
$1M nest egg
75% equities
25% commercial paper
30 year horizon
0.18% expense ratio
Initial withdrawal rate = $40,000
FIRECALC probability of success = 100%
Average terminal value =$4,218,464
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Example: (Case 2)
Investor has:
remaining mortgage balance of $100K
@5%
for 10 more years
$1.1 M nest egg (original + $100K owed)
75% equities
25% commercial paper
30 year horizon
0.18% expense ratio
Initial withdrawal rate = $46,400 (case 1 + mortgage payments)
change in withdrawal by -$6440 after 10 years
FIRECALC probability of success = 100%
Average terminal value =$4,558,859
So case 2 provides equally high probability of success with a probability to increase withdrawal rate by more than 8% over case 1. Alternatively, that 8% can be used to offset items such as healthcare that increase at well over the average inflation rate.
The analysis ignores tax advantages of case 2.
When using retirement simulators like FIRECALC, we tend to focus on probability of success and safe withdrawal rate, but once acceptable SWR is achieved there is a lot of potential advantage to increasing the terminal value. That value is a relative indicator of how well you might be able to deal with unexpected inflation or other unexpected large expenses. Alternatively, it indicates a probability that you will be able to increase your SWR at some point in the future.