Here is some more feedback on the question of One-Coat Coverage. This comes from Randy, one of our great designers in our Bellevue store. He has a lot of hands-on experience with paint, so his input comes from a user perspective. I think it illustrates why the idea of One-Coat Coverage seems to set up people with unrealistic expectations:
I appreciated your blog post about paint hide. I wanted to comment that there is another flawed assumption behind the idea of one coat coverage. One coat coverage assumes that that the paint will hide in one coat but also that the application is perfect, which is hardly ever the case. It assumes that the painter is putting on a perfectly consistent film with no variation and no holidays. The only time this happens is with spraying.
One example is the many times as a painter I would be rolling out a wall, and the paint looked like it was completely covering only to come back the next morning to find small pin hole sized holidays where the paint film had shrunk back in drying that I couldn't see when it was wet.
The other issue is the performance...thicker paint film means better performance.
The paint industry has shot itself in the foot by putting this idea out there in the first place, creating an unrealistic expectation and disappointment and frustration, though it is what people would like to hear.
Anyway, my two cents.