The whole point of FIRE is recognising when you have enough, rather than mindlessly accumulating. If your property portfolio has reached the point at which you are most happy with it, then of course you should stop there.
I'm risk averse and so my inclination would always be to pay off debt: paid-off property is a level of security in uncertain times that not much else can match. My grandparents survived the Great Depression with 4 children mostly because they had a few paid-off, very basic (later demolished) rental homes. Because they were paid off it didn't matter that the rents coming in were low and getting lower through the depression. The potential problems are if environmental conditions turn against you (flood, coastal erosion, earthquake, forest fire, drought severe enough to limit drinking water supplies) or the area massively depopulates. You should be able to tell whether any of those are a likely risk for you.
In your case, I think you should start by looking at your overall picture. You don't say what proportion of your wealth is in property and what is in equities/bonds/pensions/social security. If you look at the balance of your whole asset picture then you will get an idea of where to put further investment: do you think you are overinvested in any one area or underinvested in another? But on the whole I would certainly put at least some money into paying off the property debt, the only question I think is whether you should be sending some to other investments as well, and I like kenmoremm's idea of the debt snowball.