If your variables have several hundred lines wide scopes, you've got a problem. Such a variable is just very very very slightly better than an outright global.
Agreed, totally - and it's not an error that an experienced programmer is going to commit. But that can be said of many, if not most, errors that "warnings" catches - and we typically tell people to "always - yes, ALWAYS - enable warnings." I'm saying that this is a dangerous error, and one that should be noted and treated as such rather than some minor, optional after-thought.
I hate storms, but calms undermine my spirits.
-- Bernard Moitessier, "The Long Way"