If the child doesn't intend on moving back, well, it is time to put on their adult pants and learn to live like an adult. I mean, isn't that how they are acting with their decisions? Like an adult?
Even in the offside chance that c/s would continue, it would be substantially reduced because the costs associated with the child would otherwise be covered under s7 expenses. So the CP would receive a marginal amount, even if they were successful in challenging it.
The CP holding a room on the off chance the kids relationship may go south during the school year, is nothing more than wishing on a star. The result may happen, it may not. C/S should not continue based off of maybe's, especially when all intentions point in another direction.
I see where you are going, but your position is based off of assumptions. And should your assumption be wrong, should the NCP be reimbursed for C/S paid during the period where the child removed themselves from the care of the parents? Do you believe that most CP's would willingly reimburse the NCP should the child never return? I doubt it. And that is why C/S should cease when the child expresses their intent to remove themselves from their parents charge. If it happens they come back, c/s would resume. Because if they don't, the NCP just donated thousands of $$ to the CP for nothing.