@big_owl When you are at the point of FIRE, and you have more than enough money, it is all about optimizing money for happiness, not optimizing money for getting more money. Most people like reducing risk overall when they have "much more than enough".
Some things in life that will improve by paying off the mortgage:
1) You will make your life simpler with one less (large) payment to babysit. Even on autopilot, most of us are watching to ensure that there is always sufficient funds in the right account for the mortgage.
2) Your expenses per month are greatly reduced, providing a lot more time before you need to withdraw in a down market. Selling at a loss from time to time is normal, but stressful during retirement. This gives you time for the market to rebuild, if you choose to wait it out.
3) Fewer decisions needed in when to sell to cover your expenses. Without a mortgage, your SS or other monthly income streams may be enough to get by and you only draw down a smallish sum once a year for "fun" things like vacations.
4) In the event that you sell, die, divorce or move away, no mortgage makes this process a lot cleaner / easier as well.
5) As we age, monitoring transacations can become more difficult to track.
6) In my case, my mortgage needs renewal every 5 years, and it was stressful last time to "validate income" while FIRED, using a very low income and our investments. Banks are not set up to recognize asstes when you renew a mortgage. It becomes more complex for them and more expensive for you. Very stressful to me over a 3 month period to go through all that work of renewal. I am seriously thinking of paying it off in full at the next renewal time to avoid this.
No Mortgage => Fewer buys / sells / monitoring bank accounts on a "need to" basis ==> more mind space for pursuing happiness.
That's my opinion, obviously. The $140k amount you are talking about won't make a significant difference to your net worth, but monitoring the above monthly / quarterly, whatever, certainly will decrease life enjoyment in retirement.
The key disadavantage to paying off the mortgage, in addition to the money increases missed:
1) That money is not just sitting in a fund for you to draw down in emergencies, and you can't just get a random line of credit on your property at low rates when you have low income. Lines of credit require income to set up.
So -- Get a line of credit on your home after you pay off the mortgage, and before you retire.ETA -- you need to change your topic title from "Putting FIRE on hold to pay off mortgage" to "Paying off Mortgage early to enjoy life more in FIRE". I think your title got people thinking that you need more $$ to FIRE, but that is not the case here.