The "standard" could be offered in line pairs per mm or MTF, but it would depend on other factors like enlargement and viewing distance.

Much really depends on the design of the lens. Some lenses like the Angulon I mentioned above (not the Super-Angulon or later versions) or meniscus lenses have a very rapid drop in resolution and really can't be used beyond the circle of good definition unless you are going for an effect (like Sally Mann, for instance). Others, like some early ultra-wide designs might show a smoother and less severe decline in definition at the corners that can be quite tolerable.

This image, for instance, was made on an 8x10" camera with a pre-war 120mm/f:14 Berthiot Perigraphe at f:44:

http://www.echonyc.com/~goldfarb/photo/79bb.jpg

This lens just covers (illuminates) 8x10". If you look at a print or the negative with a loupe, you'll notice visible coma in the corners, but it's not such a distraction really. I can work with it.

On the other hand, I was looking at some 5x7" negs that a friend made with a 90mm Angulon, and the sudden loss of sharpness at the edges was just unacceptable. It was as if the photograph had been made through a Coke bottle that was drilled out in the center.