I got an AIO 28 gallon tank in april, I find with this tank maintenance is comparable to a fresh water tank, with the exception of making the water. 5-10 minutes a day when I don't test, 1/2 hour if I do a few tests at the same time. Water changes are about the same. if you have everything ready to go it doesn't take too long.
It's kinda like cleaning a house, a little bit every day saves you from having to spend hours on it all at once.
as for larger SW tanks I cannot say as I have been told I have to budget for a bright shiny object for the boss before I get one of those...
