Me too. I'm down to two litter boxes for two cats and one rarely gets used.When I had 2 cats I had 2 boxes for awhile. They both seemed to like to share 1 box, so I got rid of the second.
When I got 3 cats I decided to try the second box again. But while one cat would sometimes go in the second box, they mostly all used one box. So I got rid of the second box again and just have the one box for 3 cats. It's more scooping. I scoop 2 times per day most days, but sometimes I scoop 3 times.
I think adding extra litter boxes is good for trouble-shooting problems, but if things are fine I don't see why you would go and shake things up.