The discussion from The Waterfall Metaphor as Metaphor, boiled down to two heuristics.
1. Implicit metaphors like Good is Up have influence, so be alert to whether you’re triggering them unintentionally. Lakoff and Johnson’s *Metaphors We Live By 
* will provide you with a checklist of sorts.
2. If you don’t assign a guiding metaphor, there’s a good chance your reader will: that’s how we got “waterfall.”