I think it all depends on the cat. Tibby and Corkscrew love being with each other. And even with my RB cat Zasper my life became so much easier when I added Corkscrew into the house. She calmed down so much and seemed to be much happier because she had a play buddy now to entertain her while I was away. She became less destructive, when I would leave the house she would get bored and destroy things but when we added another cat all that stopped. After Zasper died Corkscrew became very loney and so we got Tibby for him and those two are inseperable. I think they would be sad if they didn't have each other.