Look at those faces!!! How sweet!

When I added a second cat I got two litter boxes. The E's commenced the "Battle of the Pans!" Three/four years later I still have two boxes...although right next to each other.

It wouldn't hurt to try. Maybe if he has his own personal box he won't worry about his scent going away when you change the litter.

And perhaps leaving just a bit of HIS dirty litter in the pan. When we moved I brought along a little bit of "used" litter for the pans in the new house so it would smell like home.