Good point Axe, depending in the pattern of the texture itself, will determine the offset.

The "more abstract" the pattern/texture the less you need to offset, I would never go "less" than 10 pixels thou.

A good way to test your work (blending the seams) is to run the filter again (you can repeat this almost full circle if you run it enough times!) and see if it looks right.

:)
retrocity