Like other here I think 13 miles may be generous for city driving but pretty reasonable for highway.

With that said, it works MUCH better for me than it did a couple years ago and I find most of the time I disengage it is not because it actually needed human intervention but because it wasn't aware of the social norms at certain intersections.

For example, I have an intersection near my house that requires you to inch out and essentially floor it first chance you get if you want any hope whatsoever of taking a left hand turn, but FSD will (understandably, I think) not do that.