One would live far longer on a milk-only diet than a water-only diet, I would guess. Excepting cases of pre-existing physiological dysfunction (kidney failure, lactose intolerance, etc.)

I stopped drinking milk a few years back, and lost 40 pounds after switching to water.

Milk is nutrient and calorie dense, but is linked to weight gain and acne. Milk is also slightly acidic and can cause heartburn.

@Sodra slightly acidic foods don't cause heartburn because the stomach is already intrinsically much more acidic than any common food. I'd be much more concerned about eating chips and toast other abrasive things that might damage the stomach lining if they're not perfectly chewed before swallowing.