It gets very long when all of the capacitors are used, a rough estimate being 1/60th.
If you use 1/250th instead, you'll loose brightness, but as mentioned, there will be a gradient visible on a seamless backdrop. With a Nikon FX, look for darker tones at the top of the picture. In portrait mode, it will possibly be more disturbing, left or right, depending how you hold the camera. Problem is possibly lessened with a DX camera.