A metaphor ceases to be apt when a good portion of your audience interprets your meaning in the opposite way that you intended.

I suppose whether that's true depends on whether you are looking for a metaphor that is technically accurate and descriptive or one that is perceived as such by your audience.

I'm aware that there is value in both of those, and as such am willing to strive for both, but moreso to the extent that I trust that those with whom I am communicating are doing the same. In this case, I'm not sure that good faith is there.