My wife was lactose intolerant for a number of years. Her situation was different in two key ways from what I hear from other people. First, she both grew into it and grew out of it. The condition came on during her childhood but then eased up after young adulthood. Second, her symptoms followed a pattern similar to an allergy. She could eat small amounts of dairy and be okay, like being exposed to low levels of an allergen and not having a reaction. But when her exposure crossed a certain threshold her intolerance would "trigger". Past that point she'd have strong reactions to any tiny increment of dairy, and would have to avoid it altogether for a few days until her system calmed down.