Cant wait for my 1000hz monitor!
It weighed a tonne and took up quite a lot of desk.
I would consider that approximately the upper bound.
That puts the threshold for basic perception much higher; you may not be able to see the details of the objects flashed at you for 1/500 of a second, but you can tell that something was flashed. If a bright light is strobing at 500Hz, you can tell it's strobing, not just on.