I did a bunch of experimentation when working on Folly, trying out a bunch of classic games, and the smallest width that didn’t render any of them unplayable was 64 chars. (And nearly all games were much smaller than that.) I remember Christminster in particular having a pretty wide ASCII-art map.
Obviously nobody is targeting my little interpreter, but it does imply that you’re wandering into uncharted territory if you go much wider than 64 chars or so.