I don't watch my 55g too much unless the kribs have fry with them, mostly because the tank is in a room I don't go into much. I inspect my planted tanks every time I walk by, and I make special trips to visit them too. My little 2.5 g is the most interesting. I love watching the plants and the inverts grow. My betta flares at me if I stay too long though. Jerk.
I even watch the bare 10 g snail breeding tank in my bedroom for at leat 15 mins before bed. It's fun to watch them pile on top of the wafers.
I've never though about how much time I watch them. At least an hour. And many more hours thinking about them.
I just want my planted tanks to be perfect. Is that so much to ask?
55g: (Mostly) African riverine species: Alestes Chaperi, breeding pair of Kribs, and rhino pleco
30g: Newly established reef tank
10g: Planted but fishless
5g: Unplanted with various snail species
2.5g: Heavily planted with betta.