As long as isn't really used for exceptions. Well, maybe in things like "You can have ice cream <em>as long as </em>you eat your veggies." Then it's a little like saying "You can have ice cream <em>if </em>you eat your veggies"
But "You can have ice cream, <em>but </em>you need to eat your veggies first."
Except "Everyone can have ice cream, except for Gally"