I think it depends on whether the person with DI is taking desmopressin or not. I have to drink much more water (I crave much more water!) if I am not taking my medication. When I am taking desmopressin, I drink slightly more water than my friends do and use the restroom slightly more frequently than them. But I wouldn't say it's affected my quality of life either way. The biggest improvement of quality of life for someone with DI comes from taking the appropriate dosage of desmopressin. When they take it, they will not have to wake up in the night to get water and go to the bathroom as often.