It's a lot depending on the formulas you're using, the amount of anti-aliasing you want (normally a value of two) and the resolution. I've been doing mine at a resolution of 6500x6500 at an anti-aliasing of 2 which makes it equivalent to 13000x13000.



For this particular render, it took only a couple of hours I think since it wasn't that high and the formulas used didn't take that long to render.