Lol, well, since I'm a sahm, and my house has been a mess since we got our tank, I'd say way too darn much. In fact, while typing this message, I glanced at my tank no less than 6 times. Though, I think my kids and I sit and stare at our tank probably around 4 hours a day. We make up stories about the fish and try to imaging what they are saying to each other.
It's hard to quantify ... but I gaze at my tanks really all the time when I'm in my room (where the tanks are located). Even when I am studying, reading for school, doing schoolwork, or just reading for leisure - I glance at my tanks every once in a while to see what my angels are doing, or what the fry are doing, and to see if everything is all right. Or when I have something heavy on my mind, I just look at my tanks and I'm feeling better already! LOL, I love the calming effect that aquaria have. Have you noticed? Staring at my tank really keeps me sort of relaxed.