I think the size of the tank will factor into how much time is spent to some extent. I'm sure maintenence on my 180 is a bit more than on a 40. Just in water changes and other bi-weekly stuff, I spend about 3-4 hours every other Saturday. Daily it's about 40-60 minutes in feeding, cleaning glass, checking things out, uncovering things my goby has buried, things like that.
All of that work is very soothing and theraputic for me, plus it provides a sense of accomplishment on a daily basis.