It seems to vary for everyone. There are some on this board who have successfully re-introduced dairy after a few years. Me, I've been off dairy almost four years, and gluten-free for almost three years. I show no signs of being able to tolerate casein - I recently had a minor exposure through cc to dairy, and my symptoms were as painful as ever (severe stomach pain and nausea for three straight days, worse than a gluten reaction). I didn't, however, see the rash I usually get with dairy. This is not to discourage you, but also to not give you false hope. You may be one of the lucky ones, but for many casein intolerance is permanent.