Actually I think Scott Burns did take that sort of thing into account. I don't have a link to the aticle but some of the old timers here might remember it. I THINK it's called Eat Drink and be merry
The upshot of it is, if you want to work it into a FIRECalc scenario is: Run the Monte Carlo simulator. Set the survival rate at 80%. You will find it is almost exactly the same as the 100% survival number of the "normal" Firecalc.
Therefor it takes into account the financial possibilities and also: wars, natural disasters, your own lousy luck like getting cancer at age 45, being on the next plane to be hijacked, and on and on, meteor strike.
Like they say... it's not just about "The money"