For me this is not a straight forward answer. It depends on what handgun I am shooting and how long it has been since I was last out shooting.
I have one handgun (the first handgun I purchased) my .357 mag that I have sighted in for 100 yards (open sites). I bought it for deer hunting back in 1985 (first year it was legal in Wisconsin to hunt with a handgun). I originally had it sited for 40 yards thinking I would not take a shot at a distance longer than that.
A situation presented it self for a 70 yard shot (I missed twice while the deer stood there). The third shot dropped it on the spot. After that I knew it had the power to do the job at the longer distances. My longest kill shot has been about 85 yards but I would not hesitate to try a longer shot.
With my self defense weapons I tend to stay 20 yards and under with most of my off hand training under 10 yards. I will never win any awards for my off hand shooting but it is nice to know I can hit center mass if I needed to.