5 minutes am and pm. I have one box and 9 cats.
#1 litter is Walmart's scoopable. In 28lb box, Special Kitty is only 6 bucks and lasts my 9 over a week. Consumer reports gave it raves a few years back (said it was best on market) and Walmart is out of it most of the time because it is the choice of multi-cat homes- esp. those who foster great numbers and the shelters- they wipe out the stock the same day it comes in!
My friend does extensive rescue work spends at minimum about an hour a day- once, in the evening. But that also includes cage cleaning, food, and medication. She washes when she has time! Obviously cage boxes are washed frequently while home floor cats can go a while.
Like Jen- if it stinks, it's cuz someone neglected to cover! I always call out- "Go back and cover that!" But mostly I end up doing that!