Hi Eric, there isn't really any predefined limit.

A practical limit would have to do a lot with the shape and complexity of your curves, if you have complex wiggly curves with lots of intersections between the 2 directions of the grid, that will tend to produce a more dense surface and if you get a surface with a very large number of control points in it, that can slow things down and take up a lot of memory.

But I doubt that you will be anywhere near that point with 15 curves like you are describing...

- Michael