Sorry I was misunderstood. I was talking about the URL where the form is submitted, not the URL of the form. For the URL of the form, it's generally desirable to keep it the same all things being equal because this doesn't break other people's links.

But where it is a form submission target, the only reason to care is if you are accepting third party form submission. But we are no longer talking about hypertext resources at that point which is my main point.